Appendix B
Specifications
110
Interface Signal Timing
Before using any port after the ASCII Unit is turned on or restarted, Port 1 is assigned to the peripheral device
TERM and Port 2 is assigned to LPRT. When there is an input or output at a port, the RTS, STS, DTR, and DSR
signals are treated as described below.
Transmission from the ASCII Unit to a Peripheral Device
The default setting of the DTR signal is ON at Port 1 and OFF at Port 2. When the OPEN instruction is executed, the
condition of the DTR signal varies with the peripheral device as follows:
Peripheral device
TERM
SCRN
KEYB
COMU
LRPT
Condition of DTR
ON
OFF
ON
ON
OFF
Note ON:
HIGH
OFF:
LOW
The RTS signal will be OFF if the effective signal wire is X (normally OFF) when the OPEN instruction is executed.
If the effective signal wire is O (normally ON), the RTS signal will be ON from the execution of the OPEN instruction
until the execution of the CLOSE instruction.
When the PRINT instruction is executed, the RTS signal will be ON and the ASCII Unit will transmit data after
confirming that the CTS and DSR signals are both ON. If these signals are not ON, the ERROR indicator will be lit
and the ASCII Unit will wait for the CTS and DSR signals to be turned ON. If the CTS signal is OFF during data
transmission, the output operation of the ASCII Unit will be interrupted.
Note If the DSR or CTS signal is disabled, these signals will be ignored. However, if the CTS signal to Port 2
needs to be disabled, either turn it ON or connect Port 2 to the RTS signal.
If the CLOSE statement is executed, TERM is assigned to Port 1 and LPRT is assigned to Port 2.
The following timing chart applies if the peripheral devices are TERM and COMU when the OPEN instruction is
executed.
Port 1
Port 2
Data transmission
Data transmission
CLOSE
ON
OFF
DTR (output)
RTS (output)
DSR (input)
CTS (input)
ON
OFF
Data
OPEN
ON
OFF
ON
OFF
Always ON
Normally OFF
Check
Check
Check
Check
Always ON
Normally OFF
PRINT
completes
PRINT starts
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