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this document is provided "as is" with no warranties what soever, including any warranty of merchantability, non-in- fringement, fitness for any particular purpose, or any warrant y otherwise arising out of any proposal, specification, or sample. omnivision technologies, inc. disclaims all liability, including liability for infringement of any proprietary rights, relating to the use of information in this do cument. no license, express ed or implied, by estoppel or otherwise, to any intellectual property rights is granted herein. * third-party brands, names, and trademarks are the property of their respective owners. note: the information contained in this document is consider ed proprietary to omnivision technologies, inc. this information may be distributed only to individuals or organi zations authorized by omnivision technologies, inc. to receive said information. individuals and/or organizati ons are not allowed to re-distribute said information a pplication n ote o mni tm ision omnivision serial camera control bus (sccb) functional specification last modified: 26 february 2003 document version: 2.1 revision number date revision 1.0 06/07/00 initial release 1.01 06/08/00 nomenclature change entire document - sio1 changed to sio_c, sio0 changed to sio_d, scs_ changed to sccb_e 2.0 03/08/02 inclusion of section 3.5 documenting the 2-wire master/slave implementation where sccb_e is not available in the c amera c hip tm 2.1 02/26/03 incorporated into new template
2 proprietary to omni vision technologies version 2.1, february 26, 2003 omnivision serial came ra control bus (sccb) o mni ision 00 table of contents section 1, overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1.1 2-wire sccb interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 section 2, pin functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.1 sccb_e signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.2 sio_c . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.3 sio_d . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 section 3, data transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 3.1 3-wire data transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 3.2 transmission cycles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 3.3 suspend mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 section 4, sccb structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 4.1 master device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 4.2 slave devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 4.3 conflict-protection resistors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 4.4 suspend circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 section 5, electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 section 6, terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
version 2.1, february 26, 2003 proprietary to omni vision technologies 3 o mni ision 00 list of figures figure 1-1 sccb functional block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 figure 1-2 2-wire sccb functional block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 figure 3-1 3-wire data transmission timing diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 figure 3-2 3-wire start of data transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 figure 3-3 3-wire stop of data transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 figure 3-4 transmission phases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 figure 3-5 3-phase write transmission cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 figure 3-6 2-phase write transmission cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 figure 3-7 2-phase read transmission cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 figure 3-8 phase 1 ? id address . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 figure 3-9 phase 2 ? sub-address (3-phase write transmission) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 figure 3-10 phase 2 ? read data (2-phase read transmission) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 figure 3-11 phase 2 sub-address write transmission/phase 3 write data transmission . . . . . . . . . . . . . . 13 figure 3-12 don?t-care bit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 figure 3-13 suspend mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 figure 4-1 block diagram of the master and slaves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 figure 4-2 conflict-protection resistor connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 figure 4-3 conflict-pro tection resistors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 figure 4-4 suspend circuit - pwdn mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 figure 4-5 suspend circuit - switch mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
4 proprietary to omni vision technologies version 2.1, february 26, 2003 omnivision serial came ra control bus (sccb) o mni ision 00 list of tables table 2-1 master device pin descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 table 2-2 slave device pin descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 table 5-1 sccb electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
overview version 2.1, february 26, 2003 proprietary to omni vision technologies 5 o mni ision 1overview omnivision technologies, inc. has defined and deployed the serial camera control bus (sccb), a 3-wire serial bus, for control of most of the functions in omnivision?s family of c amera c hips tm . in reduced pin package parts, the sccb operat es in a modified 2-wire serial mode. omnivision c amera c hips will only operate as slave devices and the companion back-end interface must assert as the master. one sccb master dev ice can be connected to the sccb to control at least one sccb slave device. an optional suspend- control signal provides the capability for the sccb master device to power down the sccb system. refer to figure 1-1 for the sccb functional diagram illustrating the 3-wire connection. figure 1-1 sccb functional block diagram 1.1 2-wire sccb interface the modified 2-wire implementation allows for a sccb master device to interface with only one slave device. this 2-wire applicat ion is implemented in the c amera c hip reduced pin package products where the sccb_e signal is not available externally. refer to figure 1-2 for the functional diagram of the 2-wire implementation for the sccb interface. figure 1-2 2-wire sccb functional block diagram the 2-wire implementation requires one of the fo llowing two master control methods in order to facilitate the sccb communication. 1. in the first instance, the master device must be able to support and maintain the data line of the bus in a tri-state mode. 2. the alternate method if the master cannot maintain a tri-state condition of the data line is to drive the data line either high or low and to note the transition there to assert communications with the slave c amera c hip . master device slave device sio_c sccb_e sio_d slave device slave device sio_d sio_c master device slave device
6 proprietary to omni vision technologies version 2.1, february 26, 2003 omnivision serial came ra control bus (sccb) o mni ision 2 pin functions refer to ta b l e 2 - 1 and table 2-2 for pin descriptions of the master and slave devices, respectively, used in sccb communications. 2.1 sccb_e signal the sccb_e signal is a single-dire ctional, active-low, control signal that must be driven by the master device. it indicates the start or stop of t he data transmission. a high- to-low transition of the sccb_e indicates a start of a transmission, while the low-to-high transition of the sccb_e indicates a stop of a transmission. sccb_e must remain at logical 0 during a data transmission. a logical 1 of sccb_e indicates that the bus is idle. 2.2 sio_c the sio_c signal is a single-directional, active-high, control signal that must be driven by the master device. it indicates each transmitted bit. the master must drive sio_c at logical 1 when the bus is idle. a data transmission starts when sio_c is driven at logical 0 after the start of transmission. a logical 1 of sio_c during a data transmission indicates a single transmitted bit. thus, sio_d can occur only when sio_c is driven at 0. the period of a single transmitted bit is defined as t cyc as shown in figure 3-8 . the minimum of t cyc is 10 s. table 2-1. master device pin descriptions signal name signal type description sccb_e a a. where sccb_e is not present on the c amera c hip , this signal is by default enabled and held high. output serial chip select ou tput - master drives sccb_e at logical 1 when the bus is idle. drives at logical 0 when the master asserts transmissions or the system is in suspend mode. sio_c output serial i/o signal 1 output - master drives sio_c at logical 1 when the bus is idle. drives at logica l 0 and 1 when sccb_e is driven at 0. drives at logical 0 when the system is suspend mode. sio_d i/o serial i/o signal 0 input and outp ut - remains floating when the bus is idle and drives to logical 0 when the system is in suspend mode. pwdn output power down output table 2-2. slave device pin descriptions signal name signal type description sccb_e a a. where sccb_e is not present on the c amera c hip , this signal is by default enabled and held high. input serial chip select input - input pad can be shut down when the system is in suspend mode. sio_c input serial i/o signal 1 input - input pad can be shut down when the system is in suspend mode. sio_d i/o serial i/o signal 0 input and output - input pad can be shut down when the system is in suspend mode. pwdn input power down input
data transmission version 2.1, february 26, 2003 proprietary to omni vision technologies 7 o mni ision 2.3 sio_d the sio_d signal is a bi-directional data signal that can be driven by either master or slave devices. it remains floating, or tri-state, when the bus is id le. maintenance of the signal is the responsibility of both the master and slave devices in order to avoid propagating an unknown bus state. bus float and contention are allowed during transmis sions of don?t-care or na bits. the definition of the don?t-care bit is described in section 3.2.3 . the master must avoid propagating an unknown bus state condition when the bus is floating or conf licting. a conflict-protection resistor is required to reduce static current when the bus conflicts. the connection of the conflict-protection resistor is shown in figure 4-2 . a single-bit transmission is indi cated by a logical 1 of sio_c. sio_d can occur only when sio_c is driven at logical 0. however, an exception is allowed at the beginning and the end of a transmission. during the period that sccb_e is asserted and before sio_c goes to 0, sio_d can be driven at 0. during the period that sio_c goes to 1 and before sccb_e is de-asserted, sio_d can also be driven at 0. 3 data transmission 3.1 3-wire data transmission a graphic overview of the sccb 3-wire data transmission is shown in figure 3-1 . the sccb protocol allows for bus float and contention durin g data transmissions. writing data to slaves is defined as a write transmission, while reading data from slaves is defined as a read transmission. figure 3-1 3-wire data transmission timing diagram 3.1.1 start of data transmission the start of data transmission in the 3-wire implem entation is indicated by a high-to-low transition of sccb_e. before asserting sccb_e, the master must drive sio_d at logical 1. this will avoid propagating an unknown bus state before the transm ission of data. after de-asserting sccb_e, the master must drive sio_d at 1 for a defined period again to avoid unknown bus state propagation. this period, t psa , is defined as the post-active time of sccb_e and has a minimum value of 0 s. two timing parameters are defined for the start of transmission, t prc and t pra . the t prc is defined as the pre-charge time of sio_d. this indicates the period that sio_d must be driven at logical 1 prior to assertion of sccb_e. the minimum value of t prc is 15 ns. the t pra is defined as the pre-active time of sccb_e. this indicates the pe riod that sccb_e must be asserted before sio_d sccb_e sio_c sio_d start of transmission stop of transmission d7 d6 d5 d4 d3 d2 d1 d0 x
8 proprietary to omni vision technologies version 2.1, february 26, 2003 omnivision serial came ra control bus (sccb) o mni ision is driven at logical 0. the minimum value of t pra is 1.25 s. the 3-wire start of transmission is shown in figure 3-2 . figure 3-2 3-wire start of data transmission 3.1.2 stop of data transmission a stop of data transmission is indicated by a lo w-to-high transmission of sccb_e. two timing parameters are defined for the stop of transmission, t psc and t psa . the t psc is defined as post-charge time of sio_d. it indicates the period that sio_d must remain at logical 1 after sccb_e is de-asserted. the minimum value of t psc is 15 ns. the t psa is defined as the post-active time of sccb_e. it indicates the period that sccb_e must remain at logical 0 after sio_d is de-asserted. the minimum value of t psa is 0 ns. the 3-wire stop of transmission is shown in figure 3-3 . figure 3-3 3-wire stop of data transmission sccb_e sio_c sio_d start of transmission t pra t prc sccb_e sio_c sio_d stop of transmission t psc t psa
data transmission version 2.1, february 26, 2003 proprietary to omni vision technologies 9 o mni ision 3.2 transmission cycles a basic element of a data transmission is called a phase. this section describes the three kinds of transmissions: ? 3-phase write transmission cycle ? 2-phase write transmission cycle ? 2-phase read transmission cycle 3.2.1 transmission phases a phase contains a total of 9 bits. the 9 bits consist of an 8-bit sequential data transmission followed by a ninth bit (see figure 3-4 ). the ninth bit is a don?t-care bi t or an na bit, depending on whether the data transmission is a write or read. the maximum number of phases that can be included in a transmission is three. the most significant bit (msb) is always asserted first for each phase. figure 3-4 transmission phases 3.2.1.1 3-phase write transmission cycle the 3-phase write transmission cycle (see figure 3-5 ) is a full write cycle such that the master can write one byte of data to a specific slave(s). the id address identifies the specific slave that the master intends to access. the sub-address identifies the register location of the specified slave. the write data contains 8-bit data that the master intends to overwrite the content of this specific address. the ninth bit of the three phases will be don?t-care bits. figure 3-5 3-phase write transmission cycle 6 5 4 3 2 1 0 x 7 6 5 4 3 2 1 0 x 7 6 5 4 3 2 1 0 x 7 phase 3 phase 2 phase 1 phase 1: phase 2: phase 3: id address sub-address / read data write data x x x phase 3 phase 2 phase 1 id address sub-address write data
10 proprietary to omni vision technologies version 2.1, february 26, 2003 omnivision serial came ra control bus (sccb) o mni ision 3.2.1.2 2-phase write transmission cycle the 2-phase write transmission cycle is follow ed by a 2-phase read transmission cycle. the purpose of issuing a 2-phase write transmission cycle (see figure 3-6 ) is to identify the sub-address of some specific slave from which the master intends to read data for the following 2-phase read transmission cycle. the ninth bit of the 2-phas e write transmission will be don?t-care bits. figure 3-6 2-phase write transmission cycle 3.2.1.3 2-phase read transmission cycle there must be either a 3-phase or a 2-phase wr ite transmission cycle as serted ahead of a 2-phase read transmission cycle. the 2-ph ase read transmission cycle (see figure 3-7 ) has no ability to identify the sub-address. the 2-phase write transm ission cycle contains read data of 8 bits and a ninth don?t-care bit or na bit. the master must drive the na bit at logical 1. figure 3-7 2-phase read transmission cycle x x phase 2 phase 1 id address sub-address x na phase 2 phase 1 id address read data
data transmission version 2.1, february 26, 2003 proprietary to omni vision technologies 11 o mni ision 3.2.2 phase descriptions the following sections describe the individual phases found in the various transmission cycles. 3.2.2.1 phase 1 ? id address phase 1 is asserted by the master to identify the selected slave to which the data is read or written. each slave has a unique id address. the id addres s is comprised of seven bits, ordered from bit 7 to bit 1, and can identify up to 128 slaves. the eighth bit, bit 0, is the read/write selector bit that specifies the transmission direction of the current cycle. a logical 0 represents a write cycle and a logical 1 represents a read cycle. the ninth bit of phase 1 must be a don?t-care bit. sio_d_oe_m_ and sio_d_oe_s_ shown in figure 3-8 are internal active-low, i/o-enabled signals in the master and slave(s), respectively. sio_d_oe_s_ transaction occurs before the transition of sio_d_oe_m_, as shown in figure 3-8 . the master asserts the id address, but de-assert s the ninth bit (don?t-care bit). the master must mask the input of sio_d during the period of the don?t-care bit and force the input to 0 to avoid propagating an unknown bus state. the master cont inues asserting the following phases regardless of the response to the don?t- care bit by the slave(s). the sio_oe_s is controlled by the slave(s) and may remain at logical 1 or be driven at logical 0. the bus may be in a floating or conflicting status du ring the transmission of the don?t-care bit. in this case, it is the slave?s responsibility to avoid propagating an unknown bus state. a detailed description of the d on?t-care bit is described in section 3.2.3 . figure 3-8 phase 1 ? id address sccb_e sio_c sio_d sio0_oe_m_ sio0_oe_s_ phase 1 t cyc 0: write 1: read d7 d6 d5 d4 d3 d2 d1 r/w d7 x
12 proprietary to omni vision technologies version 2.1, february 26, 2003 omnivision serial came ra control bus (sccb) o mni ision 3.2.2.2 phase 2 ? sub-address/read data either the master or the slave(s) may assert a phase 2 transmission. a phase 2 transmission asserted by the master identifies the sub-address of the slave(s) the master intends to access. a phase 2 transmission asserted by t he slave(s) indicates the read data that the master will receive. the slave(s) recognize the sub-address of this read data according to the previous 3-phase or 2-phase write transmission cycles. the ninth bit is defined as a don?t-care bit when the master asserts phase 2. sio_d_oe_m_ and sio_d_oe_s_ are the same as those defined under section 3.2.2.1 . the detailed timing is illustrated in figure 3-9 . figure 3-9 phase 2 ? sub-address (3-phase write transmission) the ninth bit is defined as an na bit when the slave(s) assert the phase 2 transmission. sio_d_oe_m_ is de-asserted from the ninth bit of phase 1 and re-asserted for the na bit. the master is responsible for driving sio_d at logica l 1 during the period of the na bit. concurrently, sio_d_oe_s_ is asserted. the selected slave is responsible for driving sio_d during the read data period. since sio_d_oe_s_ is de-asserted before sio_d_oe_m_ is asserted during the period of the na bit, bus float of sio_d occurs when the master tries to drive the na bit. the detailed timing is shown in figure 3-10 . figure 3-10 phase 2 ? read data (2-phase read transmission) sccb_e sio_c sio_d sio0_oe_m_ sio0_oe_s_ phase 2 x d7d6 d5d4d3 d2d1 x d0 d7 sccb_e sio_c sio_d sio0_oe_m_ sio0_oe_s_ phase 2 x d7 d6 d5d4d3d2 d1d0
data transmission version 2.1, february 26, 2003 proprietary to omni vision technologies 13 o mni ision 3.2.2.3 phase 3 ? write data only the master may assert the phase 3 transmissi on. the phase 3 transmission contains the actual data the master intends to write to the slave(s). the timing diagram shown in figure 3-11 applies to both phase 2 sub-address write transmissi ons and phase 3 write data transmissions. the ninth bit of the phase 3 transmission is defined as a don?t-care bit since the master is asserting the transmission. sio_d_oe_m_ and sio_d_oe_s_ are the same as those defined for a phase 1 transmission. figure 3-11 phase 2 sub-address write transmission/phase 3 write data transmission 3.2.3 don?t-care bit the don?t-care bit is the ninth bit of a master-issued transmission (id address, sub-address, and write data). the master will continue to assert transmission phases until the transmission cycle is complete. the master also assumes that there is no transmission error dur ing data transmissions. the purpose of the don?t-care bit is to indicate the completion of the transmission. when there is more than one slave on the bus, the slave(s) may respond to the don?t-care bit in one of two ways. if slave 1 is selected and data is written to this specific slave, slave 1 will drive sio_d to logical 0 for the don?t-care bit. in this case, the sio_d signal may conflict at the beginning of the don?t-care bit, while it may be float ing at the end of the don?t-care bit (see figure 3-12 ). alternately, it is possible that the slave(s) do not respond to the don?t-care bit of the current phase. in this situation, the sio_d bus remain s at float for the whole don?t-care bit. the master does not check for transmission errors during data transmissions. there is a provision for the slave(s) to record the status of the don?t-care bit in an internal register as shown in the following example: a slave(s) has defined a 1 byte register as the do n?t-care status register. the default value of the don?t-care status register is defined as 55. assuming there are no errors during the data transmission, this register value will re main unchanged. if t he slave does not receive the don?t-care bit, the register value will change to 54. sccb_e sio_c sio_d sio0_oe_m_ sio0_oe_s_ x d7d6 d5d4d3 d2d1 x d0 phase 2/phase 3
14 proprietary to omni vision technologies version 2.1, february 26, 2003 omnivision serial came ra control bus (sccb) o mni ision the master may query the don?t-care status regi ster to determine if there has been a transmission of data. the master will issue an additional read tran smission to the don?t-care status register in the target slave to check the value and, subseq uently, determine if an error has occurred. this scheme will not determine an error if the entire sccb circuit has been corrupted. sio_d_oe_m_ can be de-asserted and re-asserted during the don?t-care bit transmission only when sio_c is driven to logical 0. the t mack is defined as the period of de-assertion of sio_d_oe_m_ prior to the low-to-high transition of sio_c during the don?t-care bit transmission. the period of re-assertion of sio_d_oe_m_ after the high-to-low transmissi on is also defined as t mack . the minimum value of t mack is 1.25 s. if a slave intends to respond to the don?t-care bit, sio_d_oe_s_ can be asserted and de-asserted during the don?t-care bit transmission only wh en sio_c is driven to logical 0. the t sack is defined as the period of assertion of sio_d_oe_s_ occu rring after the high-to-low transition of sio_c at the beginning of the don?t-care bit transmission. the period of de-assertion of sio_d_oe_s_ occurring after the high-to-low trans ition at the end of the don?t-care transmission is also defined as t sack . the minimum value of t sack is 370 ns. figure 3-12 don?t-care bit sccb_e sio_c sio_d sio0_oe_m_ sio0_oe_s_ d0 x d7 t mack t mack t sack t sack float conflict
data transmission version 2.1, february 26, 2003 proprietary to omni vision technologies 15 o mni ision 3.3 suspend mode suspend mode (see figure 3-13 ) is determined by the dedicated pw dn_ pin of the master. this is achieved by the active-low outpu t signal that specifies the su spension period as the master attempts to power down the system. during the suspension period, sccb_e, sio_c, and sio_d are all driven to logical 0 by the master in order to avoid current leakage. there must be some time for pwdn_ to be asserted prior to and be de-asserted after the assertion of sccb_e, sio_d, and sio_c. this parameter is defined as t sup . the minimum value of t sup is 50 ns. this scheme can prevent logical errors from occurring in sccb slaves. the pwdn pin in slaves has the opposite polarity of the pwdn_ pin of the master. two control schemes for suspending the slave(s) are described in section 4.4 . figure 3-13 suspend mode sccb_e sio_c sio_d pwdn_ suspend t sup t sup
16 proprietary to omni vision technologies version 2.1, february 26, 2003 omnivision serial came ra control bus (sccb) o mni ision 4 sccb structure the structure of the sccb system is shown in figure 4-1 . this diagram illustrates the connection of one master with one slave. multiple slaves may be connected on the same bus. a conflict-protection resistor of sio_d is required for each slave. connection of conflict-protection resistors for multiple slaves is illustrated in figure 4-3 . figure 4-1 block diagram of the master and slaves 4.1 master device the master device drives both sccb_e and sio_c signals, while either the master or slave(s) can drive the sio_d signal. during the de-assertion of sccb_e, the master must block the sio_d input to avoid propagating unknown bus conditions due to bus float. during the don?t-care bit transmission, the master must ignore the status of sio_d and keep asserting the subsequent phases. the pwdn_ is driven by the master to indica te the suspend mode cycle. as noted in section 4.4 , there are two different ways to implement suspension circuits within the system. 4.2 slave devices the slave(s) receive the sccb_e and sio_c signals from the master, while either the master or the slave(s) can drive sio_d. input pads of the sccb_e, sio_c, and sio_d signals contain the standby (stby) control terminal for reducing leak age current when the inputs are floating. output terminals of those input pads are driven at logica l 1 when stby is asserted. this can avoid logical errors during suspend cycles. master device sccb master sio_d_oe_m_ pwdn_ pwdn slave device sccb_e sio_c sio_d sccb slave sio_d_oe_s_ stby stby stby
sccb structure version 2.1, february 26, 2003 proprietary to omni vision technologies 17 o mni ision pwdn controls stby of sccb_e. this means the output terminal of the sccb_e input pad is driven at logical 1 during suspend mode cycles even though the master drives the input of sccb_e at 0. the stby control terminals of both sio_c and sio_d are controlled by pwdn and sccb_e. during suspend mode cycles and the de-assertion of sccb_e, the output terminals of sio_c and sio_d input pads are both driven at logical 1. du ring the don?t-care bit tr ansmission, the slave(s) must avoid propagating unknown bus conditions. 4.3 conflict-prot ection resistors incorporating series resistors between sio_d output of the master and the sio_d input of the slave(s) can avoid short circui ts when bus contention occurs. figure 4-2 conflict-protection resistor connections figure 4-3 conflict-protection resistors master device slave device master device master device slave device slave device sio_d sio_d sio_d sio_d master slave master slave 1 0 1 0
18 proprietary to omni vision technologies version 2.1, february 26, 2003 omnivision serial came ra control bus (sccb) o mni ision 4.4 suspend circuits there are two methods of issuance of a bus suspend cycle: ? pwdn mode ? switch mode 4.4.1 pwdn mode the power pads of the slave(s) are always connected to vdd. the pwdn_ signal from the master device needs to be inverted prior to connection to the slave(s) and the slave(s) circuit has an opposite polarity. during normal operations, pwdn_ of the master is driven at logical 1 and the npn transistor is on. in normal operation, the pwdn of the slave(s) is driven at logical 0. during the suspend mode cycle, pwdn_ is driven at 0 and the npn transistor is off. during the suspend mode operation, the pwdn of the slave(s) is driv en at 1. there is no leakage current during the suspend cycle. figure 4-4 suspend circuit - pwdn mode vdd pwdn_ vdd pwdn sccb_e sio_c sio_d master device slave device
electrical characteristics version 2.1, february 26, 2003 proprietary to omni vision technologies 19 o mni ision 4.4.2 switch mode the pwdn circuit of the slave(s) is always connected to logical 0. a power switch circuit is required for each slave. the power of each slave is off during suspend mode cycles. in suspend mode operation, there is no leakage current present as no power is provided to the slave(s). figure 4-5 suspend circuit - switch mode 5 electrical characteristics table 5-1. sccb elec trical characteristics symbol parameter condition min max unit t cyc single bit transmission cycle time 10 s t prc pre-charge time of sio_d 15 ns t pra pre-active time of sccb_e 1.25 s t psc post-charge time of sio_d 15 s t psa post-active time of sccb_e 0s t mack sio_d_oe_m_ transition time 1.25 s t sack sio_d_oe_s_ transition time 370 ns t sup pwdn_ pre/post-charge time 50 ns vdd pwdn_ vdd pwdn sccb_e sio_c sio_d master device slave device
20 proprietary to omni vision technologies version 2.1, february 26, 2003 omnivision serial came ra control bus (sccb) o mni ision 6terminology don?t-care bit: ninth bit of a write phase. id address: unique address of each device on the bus. the master asserts the slave id address to identify transmissions destined for the slave device(s). na bit: ninth bit of a read phase. phases: a phase contains a total of 9 bits consisting of a sequential transmission of 8 data bits followed by a ninth don?t-care or na bit, depending on writes or reads. read phases: phases that read data from slave(s). read transmissions: master-asserted transmissions which read data from slave device(s). sccb data transmissions: transmissions consist of phases. all transmiss ions are initiated by the master device. start and stop of a transmission in the 3-wire system are indicated by the signaling of sccb_e. start and stop of a transmission in the 2-wire system are indicated by signaling of the sio_d. sccb_e: serial bus enable/disable signal, previously denoted as scs_, sccbb, and iicb in older documentation. sccb master device: an sccb device that can assert sccb transmissions. only one master is allowed in the system. sccb slave device(s): sccb device(s) that can respond to an asserted sccb transmission. at least one slave can be connected to the system. sccb system: system consists of one master and at least one slave. serial camera control bus: typically, a 3-wire serial bus with an optional suspend-control (sccb) signal. may be implemented in a 2-wire mode where required. sio_c: serial bus clock signal, previously denoted as sio1 and scl in older documentation. sio_d: serial bus data signal, previously denoted as sio0 and sda in older documentation.
terminology version 2.1, february 26, 2003 proprietary to omni vision technologies 21 o mni ision sub-address: the master asserts the sub-address to indicate the specific slave function/location to be accessed. suspend mode: master-asserted suspend periods of device and/or system suspension. transmission cycles: transmission cycles include 3- phase write transmission cycle, 2-phase write transmission cycle, and 2-phase read transmission cycle. write transmissions: master-asserted transmissions which write data to slave device(s).
22 proprietary to omni vision technologies version 2.1, february 26, 2003 omnivision serial came ra control bus (sccb) o mni ision note : ? all information shown herein is current as of the revision and publication date. please refer to the omnivision web site (http://www.ovt.com ) to obtain the current versions of all documentation. ? omnivision technologies, inc. reserves the ri ght to make changes to their products or to discontinue any product or service without further notice (it is advisable to obtain current product documentation prior to placing orders). ? reproduction of information in omnivision product documentation and specifications is permissible only if reproduction is without alte ration and is accompanied by all associated warranties, conditions, li mitations and notices. in such cases, omnivision is not responsible or liable for any information reproduced. ? this document is provided with no warrant ies whatsoever, including any warranty of merchantability, non-infringement, fitness fo r any particular purpose, or any warranty otherwise arising out of any proposal, specifi cation or sample. furthermore, omnivision technologies inc. disclaims all li ability, including liability for in fringement of any proprietary rights, relating to use of information in this document. no license, expressed or implied, by estoppels or otherwise, to any intellec tual property rights is granted herein. ? ?omnivision?, ?camerachip? are trademarks of omnivision technologies, inc. all other trade, product or service names referenced in this release may be trademar ks or registered trademarks of their respective holders. third-party brands, nam es, and trademarks are the property of their respective owners. for further information, please feel free to contact omnivision at info@ovt.com . omnivision technologies, inc. sunnyvale, ca usa (408) 733-3030

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