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OmniVision Technologies Seril Camera Control Bus(SCCB) Specification(OV7670资料).pdf
1 Overview
Figure 1-1 SCCB Functional Block Diagram
1.1 2-Wire SCCB Interface
Figure 1-2 2-Wire SCCB Functional Block Diagram
2 Pin Functions
Table 2-1. Master Device Pin Descriptions
Table 2-2. Slave Device Pin Descriptions
2.1 SCCB_E Signal
2.2 SIO_C
2.3 SIO_D
3 Data Transmission
3.1 3-Wire Data Transmission
Figure 3-1 3-WIre Data Transmission Timing Diagram
3.1.1 Start of Data Transmission
Figure 3-2 3-Wire Start of Data Transmission
3.1.2 Stop of Data Transmission
Figure 3-3 3-Wire Stop of Data Transmission
3.2 Transmission Cycles
3.2.1 Transmission Phases
Figure 3-4 Transmission Phases
Figure 3-5 3-Phase Write Transmission Cycle
Figure 3-6 2-Phase Write Transmission Cycle
Figure 3-7 2-Phase Read Transmission Cycle
3.2.2 Phase Descriptions
Figure 3-8 Phase 1 - ID Address
Figure 3-9 Phase 2 - Sub-address (3-Phase Write Transmission)
Figure 3-10 Phase 2 - Read Data (2-Phase Read Transmission)
Figure 3-11 Phase 2 Sub-address Write Transmission/Phase 3 Write Data Transmission
3.2.3 Don’t-Care Bit
Figure 3-12 Don’t-Care Bit
3.3 Suspend Mode
Figure 3-13 Suspend Mode
4 SCCB Structure
Figure 4-1 Block Diagram of the Master and Slaves
4.1 Master Device
4.2 Slave Devices
4.3 Conflict-Protection Resistors
Figure 4-2 Conflict-Protection Resistor Connections
Figure 4-3 Conflict-Protection Resistors
4.4 Suspend Circuits
4.4.1 PWDN Mode
Figure 4-4 Suspend Circuit - PWDN Mode
4.4.2 Switch Mode
Figure 4-5 Suspend Circuit - Switch Mode
5 Electrical Characteristics
Table 5-1. SCCB Electrical Characteristics
6 Terminology
APPLICATION NOTE
Omni
ision ®
OmniVision Serial Camera Control Bus (SCCB)
Functional Specification
Last Modified: 26 February 2003
Document Version: 2.1
Revision Number
1.0
1.01
2.0
2.1
Date
06/07/00
06/08/00
03/08/02
02/26/03
Revision
Initial Release
Nomenclature change entire document - SIO1 changed to SIO_C, SIO0
changed to SIO_D, SCS_ changed to SCCB_E
Inclusion of Section 3.5 documenting the 2-wire master/slave
implementation where SCCB_E is not available in the CAMERACHIPTM
Incorporated into new template
This document is provided "as is" with no warranties whatsoever, including any warranty of merchantability, non-in-
fringement, fitness for any particular purpose, or any warranty 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 document. No license, expressed 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 considered proprietary to OmniVision Technologies, Inc. This
information may be distributed only to individuals or organizations authorized by OmniVision Technologies, Inc. to
receive said information. Individuals and/or organizations are not allowed to re-distribute said information
OmniVision Serial Camera Control Bus (SCCB)
00Table of Contents
Omni
ision
Section 1, Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2-Wire SCCB Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.1
Section 2, Pin Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
SCCB_E Signal. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
SIO_C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
SIO_D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.1
2.2
2.3
Section 3, Data Transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3-Wire Data Transmission. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Transmission Cycles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Suspend Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.1
3.2
3.3
Section 4, SCCB Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Master Device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Slave Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Conflict-Protection Resistors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Suspend Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
4.1
4.2
4.3
4.4
Section 5, Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Section 6, Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
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Omni
ision
00List 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-Protection Resistors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Figure 4-4
Suspend Circuit - PWDN Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Figure 4-5
Suspend Circuit - Switch Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
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OmniVision Serial Camera Control Bus (SCCB)
Omni
ision
00List 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
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Omni
ision
1 Overview
Overview
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 CAMERACHIPSTM.
In reduced pin package parts, the SCCB operates in a modified 2-wire serial mode.
OmniVision CAMERACHIPS will only operate as slave devices and the companion back-end interface
must assert as the master. One SCCB master device 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
Master Device
SCCB_E
SIO_C
SIO_D
Slave Device
Slave Device
Slave Device
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 application is implemented in the CAMERACHIP 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
Master Device
SIO_C
SIO_D
Slave Device
The 2-wire implementation requires one of the following 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 CAMERACHIP.
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Omni
ision
2 Pin Functions
Refer to Table 2-1 and Table 2-2 for pin descriptions of the master and slave devices, respectively,
used in SCCB communications.
Table 2-1.
Master Device Pin Descriptions
Signal Name
Signal Type
Description
SCCB_Ea
SIO_C
SIO_D
PWDN
Output
Output
I/O
Output
Serial Chip Select Output - 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.
Serial I/O Signal 1 Output - master drives SIO_C at logical 1 when
the bus is idle. Drives at logical 0 and 1 when SCCB_E is driven
at 0. Drives at logical 0 when the system is Suspend mode.
Serial I/O Signal 0 Input and Output - remains floating when the
bus is idle and drives to logical 0 when the system is in Suspend
mode.
Power down output
a. Where SCCB_E is not present on the CAMERACHIP, this signal is by default enabled and held high.
Table 2-2.
Slave Device Pin Descriptions
Signal Name
Signal Type
Description
SCCB_Ea
SIO_C
SIO_D
PWDN
Input
Input
I/O
Input
Serial Chip Select Input - input pad can be shut down when the
system is in Suspend mode.
Serial I/O Signal 1 Input - input pad can be shut down when the
system is in Suspend mode.
Serial I/O Signal 0 Input and Output - input pad can be shut down
when the system is in Suspend mode.
Power down input
a. Where SCCB_E is not present on the CAMERACHIP, this signal is by default enabled and held high.
2.1 SCCB_E Signal
The SCCB_E signal is a single-directional, active-low, control signal that must be driven by the
master device. It indicates the start or stop of the 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 tCYC as shown in Figure 3-8. The minimum of tCYC is 10 µs.
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ision
2.3 SIO_D
Data Transmission
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 idle. 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 transmissions 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 conflicting. 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 indicated 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 during 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
Start of
Transmission
Stop of
Transmission
SCCB_E
SIO_C
SIO_D
D7
D6
D5
D4
D3
D2
D1
D0
X
3.1.1 Start of Data Transmission
The start of data transmission in the 3-wire implementation 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 transmission 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, tPSA, is defined as the post-active time of SCCB_E and has a minimum value of 0 µs.
Two timing parameters are defined for the start of transmission, tPRC and tPRA. The tPRC 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 tPRC is 15 ns. The tPRA is defined as the
pre-active time of SCCB_E. This indicates the period that SCCB_E must be asserted before SIO_D
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OmniVision Serial Camera Control Bus (SCCB)
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ision
is driven at logical 0. The minimum value of tPRA is 1.25 µs. The 3-wire start of transmission is
shown in Figure 3-2.
Figure 3-2
3-Wire Start of Data Transmission
Start of
Transmission
tPRA
tPRC
SCCB_E
SIO_C
SIO_D
3.1.2 Stop of Data Transmission
A stop of data transmission is indicated by a low-to-high transmission of SCCB_E. Two timing
parameters are defined for the stop of transmission, tPSC and tPSA. The tPSC 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 tPSC is 15 ns. The tPSA 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 tPSA is 0 ns. The 3-wire stop of transmission is shown in
Figure 3-3.
Figure 3-3
3-Wire Stop of Data Transmission
Stop of
Transmission
tPSA
tPSC
SCCB_E
SIO_C
SIO_D
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