Communication Interface - Wyse WY-60 Maintenance Manual

Table
6-2
8051 Port Assignments, Continued
Port Assignment
P1.2
P1.3
P 1.4
P1.5
P1.6
P1.7
P2.0-P2.7
P3.0
P
3.
1
P3.2 (INTO)
P3.3 (INT1)
P3.4 (TO)
P3.5 (Tn
P3.6
P3.7
EEPROM clock. This state, combined with the state
onP1.1, determines "incoming data types:
start/stop bits, acknowledgment, address, or
actual data.
/DSR AUX. Data Set Ready line on the AUX port.
/DTR AUX. Data Terminal Ready line on the AUX port.
Keyboard CMD. Command output to the keyboard.
KBD data.
MPS vertical size.
High byte of address bus.
RXD AUX. Receive Data line on the AUX port.
TXD AUX. Transmit Data line on the AUX port.
2672 BREQ. Input from the 2672 indicating that
display data transfers from RAM to the row
buffers are about to occur.
2661 INTR. Interrupt input from the 2681A.
Indicates data in the receive buffer.
2672 INTR. Interrupt input indicates the start of
vertical synchronization.
Baud rate clock.
WR strobe. I/O write signal output by 8051.
RD strobe. I/O read signal output by 8051.
Communication Interface
Both serial ports, the MODEM port and AUX port, are asynchronous.
In setup, both the MODEM and AUX ports can be independently
configured to connect to computers, modems, or printers.
MODEM Port--The
2661 UART controls the MODEM port. The MC1488
driver (U26) and the MC1489A receiver (U25) are both RS232
compatible. The 2661 (U3) converts parallel logic PCB data to
bit-serial data, while adding stop, start, and parity bits. The
serial format is transmitted at user-selected baud rate.
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