Bench-1 Computer Drawings: Reset Circuit
The primary RS-232 port is run through ACIA1, a 65C51. Of the other two ACIAs, only ACIA3 has a line driver and receiver for RS-232 connected, and only for the TD and RD lines, not for any of the handshaking lines. ACIA1 on the other hand has the full complement except for RI, which is not very often used.
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