Brother MFC-9420CN Service Manual page 76

The COMMAND signal and STATUS signal are the signals that are used to transfer the data
between the controller and the engine, which perform as a half-duplex asynchronous serial
communication. Refer to Fig.3-40.
Start bit
COMMAND
LSB
STATUS
NOTE:
•
Based on "Asynchronous communication" method.
•
Command/status communication must keep the "Handshake rule".
•
Baud rate is 9600 bps.
•
Frame format: - one (1) start bit,
- eight (8) data bits
(Start bit side is LSB, Parity bit is MSB),
- one (1) odd parity bit,
- one (1) stop bit.
•
The video controller has to send an "Initialize command" to the engine controller after power
on in order to establish communication.
The power for the main PCB is supplied through the engine interface connector.
Stop bit
Parity bit
P
MSB
8ms (TYP) 30ms (MAX)
LSB
Start bit
Fig. 3-40
3 - 4 4
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MSB
P
Parity bit
Stop bit
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