Rice Lake Okidata 320-390-420 Turbo - Service Guide - Manual (Page 23)

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Service Guide ML320/321Turbo
Chapter 2 Operation Description
2.1.7 Operation Panel
The clock synchronization OPCLK signal of the LSI is used to input the switch data and output the LED
data through the operation panel control LSI (IC1: BU5148S).
A 2-byte (15 bits + 1 even parity bit) command signal (OPTXD) is transmitted to the LSI(BU5148S) in
synchronization with the OPCLK signal. The LSI decodes this command and when it is found to be legal,
returns a 2-byte command response back to the LSI which includes data on Switch information, LED
status, receive command ACK/NAK and 1 odd parity bit.
Any transmission errors found cause the command to be reissued after the transmission of the OPCLR-N
signal.