4-3
Section
CPM2A/CPM2C Communications Functions
250
The unsolicited Host Link communications are executed using TXD(48).
Mnemonic
Control
Contents
(@)TXD(48)
Communications port
output
Reads data from I/O memory and transmits
it in the specified frame format.
Host Link communications are controlled with the following AR area flags.
Word
Bit(s)
Contents
AR 08
00 to 03
RS-232C Port Error Code
0: Normal completion
1: Parity error
2: Frame error
3: Overrun error
04
RS-232C Communications Error Flag
ON: RS-232C port communications error occurred
OFF: Normal
05
RS-232C Transmit Ready Flag
ON: The PC is ready to transmit data.
08 to 11
Peripheral Port Error Code
0: Normal completion
1: Parity error
2: Frame error
3: Overrun error
12
Peripheral Port Communications Error Flag
ON: Peripheral port communications error occurred.
13
Peripheral Port Transmit Ready Flag
ON: The PC is ready to transmit data.
Unsolicited Communications
A data transmission to the host computer is initiated by the PC.
S: Leading address of data to be transmitted
C: Control data
N: Number of bytes to be transmitted (BCD: 0001 to 0061)
Communications port
0: RS-232 port; 1: Peripheral port
(@)TXD(48)
S
C
N
When Host Link communications are being used, TXD(48) converts the N-bytes
of data starting at S to ASCII, adds the Host Link header, FCS, and terminator,
and transmits this data as a Host Link frame.
The transmitted Host Link frame will be as shown in the following diagram.
Converted to ASCII.
N bytes
Node No.
Data (ASCII)
↵
Ladder Program
(Mnemonics)