CHEETAH 3G-SDI Camera
November 16, 2017
Page
45
of
53
Rev 1.1
Figure 34: RS-232 serial protocol format
You can update each camera control register independently. The serial protocol
defines all registers as 16-bit address (hex format) and 32-bit data (hex format).
Camera registers using fewer than 32-bits in width must be padded with 0s on
writes; unused bits are ignored on reads. Register data is always packed low
within 32-bit data words for registers defined less than 32-bits.
Each command experiences delay due to command execution and data
transmission over the serial port. This latency varies from command to command
because of resource location and command response length.
6.1.1.1 Write Operation
To write to any given camera register, send a sequence of 7 bytes to the camera.
If there is no error, the camera returns a one byte acknowledge for the write
command <Ack>.
Write to camera (7 Bytes): <Write_Cmd> <Address> <Data>
1st byte: 0x57 (Write Command)
2nd byte: <Register Address_High> MSB
3rd byte: <Register Address_Low> LSB
4th byte: <Register Data Byte 4> MSB
5th byte: <Register Data Byte 3> …
6th byte
: <Register Data Byte 2> …
7th byte: <Register Data Byte 1> LSB
Write Acknowledge (1 Byte): <Ack>
1st byte: 0x06 (Acknowledge)
Figure 35: Normal write cycle
If there is an error, the camera returns two bytes not-acknowledge for the write
command
–
the first byte is <Nac> <Err>, the second is the error code as shown
in the following diagrams:
Write Not-acknowledge (2 Bytes): <Nak> <Error Code>
1st byte:0x15 (Not-acknowledge)
2nd byte: <XX> (Nck Error Code. See Error Code Description section)
