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2.
Main Logic Board
2-1. Data I/O Circuitry
The main logic board relays data back and forth to the host computer via the interface board.
2-1-1. RS-232C Interface
CN3
DTR
R-CH
TXD
RXD
CTS
Data from host to printer passes through the IC1 on the interface board from the RXD terminal and is input to the CPU on
the main logic board.
IC1 converts the RS-232C and TTL voltage levels.
The CPU converts the input serial data to parallel data and stores that data in the memory buffer memory. It also converts
the internal parallel data to serial data and outputs that to the IC1.
The CTS line is hardware-connected, but the connection is not recognized by software. (The printer does not monitor the
signal.)
IC1
D2O
D2I
D1O
D1I
R1I
R1O
R2I
R2O
HD151232FP
RS-232C Interface Board
Fig. 2-2 RS-232C Interface
– 18 –
IC10
CN1
CN9
Gate
Array
B12
B12
ACK
B14
B14
A15
A15
B15
B15
Main Logic Board
IC5
CPU
TXD0
RXD0
RXD1
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