Operation Panel - OKIDATA ML590 Service Manual

Page: 62
Service Guide ML590/ML591
Chapter 2 Principles of Operation

2.1.07 Operation Panel

The Serial I/O Port (Ports 20 - 23) of the MPU reads the operation panel switch data from the
operation panel control LSI (Location IC1: BUS148S). The Serial I/O Port also outputs LED data
to the operation panel control LSI.
A two byte (15 bits +1 parity bit (even parity)) command (OPTXD) is transmitted from the MPU to
the operation panel LSI in synchronization with the OPCLK signal. Once the LSI decodes the
command, the command must pass a command code check and have no parity errors. Then, the
specified I/O control will return the two byte command response to the MPU.