Computer Hardware User Manual

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Note RXD(––) is required to receive data via the peripheral port or RS-232C port only.
Transmission sent from a host computer to a Host Link Unit are processed auto-
matically and do not need to be programmed.
Caution The PC will be incapable of receiving more data once 256 bytes have been re-
ceived if received data is not read using RXD(––). Read data as soon as pos-
sible after the Reception Completed Flag is turned ON (SR 26414 for the periph-
eral port, SR26406 for the RS-232C port).
Control Word The value of the control word determines the port from which data will be read
and the order in which data will be written to memory.
Byte order 0: Most significant bytes first
1: Least significant bytes first
CTS and DSR signal monitoring
0: Don’t monitor CTS and DSR signals.
1: Monitor the CTS signal. (Output to bit 15 of D.)
2: Monitor the DSR signal. (Output to bit 15 of D.)
3: Monitor the CTS and DSR signals. (Output to bits 15 and 14 of D.)
Auxiliary reception port (when DR-15 is 0.)
0: Internal RS-232C port
1: Communications port A
2: Communications port B
Port 0: RS-232C port
1: Peripheral port
Digit number: 3210
The order in which data is written to memory depends on the value of digit 0 of C.
Eight bytes of data 12345678... will be written in the following manner:
MSB LSB
D12
D+1 3 4
D+2 5 6
D+3 7 8
Digit 0 = 0
MSB LSB
D21
D+1 4 3
D+2 6 5
D+3 8 7
Digit 0 = 1
Flags ER: The CPU Unit is not equipped with an RS-232C port.
Another device is not connected to the specified port.
There is an error in the communications settings (PC Setup) or the oper-
and settings.
Indirectly addressed DM word is non-existent. (Content of DM word is
not BCD, or the DM area boundary has been exceeded.)
The destination words (D to D+(N÷2)–1) exceed the data area.
Peripheral Port
26414: SR 26414 will be turned ON when data has been received normally at
the peripheral port and will be reset when the data is read using
RXD(––) is executed.
266: SR 266 contains the number of bytes received at the peripheral port and
is reset to 0000 when RXD(––) is executed.
RS-232C Port
Serial Communications Instructions Section 5-27