Star Micronics TUP400 Series, Technical Manual

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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
Fig. 2-2 RS-232C Interface
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.)
D2O
D1O
R1I
R2I
D2I
D1I
R1O
R2O
B12
B14
A15
B15
ACK DTR
R-CH
TXD
RXD
CTS
TXD0
RXD0
RXD1
CN3 CN1
IC1
CN9
IC10
IC5
Gate
Array
CPU
HD151232FP
RS-232C Interface Board Main Logic Board
B12
B14
A15
B15