17: USER COMMUNICATION INSTRUCTIONS
« FC4A MICROSMART USER’S MANUAL » 17-7
User Communication Transmit Instruction Dialog Box in WindLDR
Selections and Operands in Transmit Instruction Dialog Box
Transmit Data
Transmit data is designated by source operand S1 using constant values or data registers. BCC code can also be calculated
automatically and appended to the transmit data. One TXD instruction can transmit 200 bytes of data at the maximum.
S1 (Source 1)
Designating Constant as S1
When a constant value is designated as source operand S1, one-byte data is transmitted without conversion. The valid
transmit data value depends on the data bits selected in the Communication Parameters dialog box, which is called from
Configure > Fun Area Settings > Communication, followed by selecting User Protocol in Port 1 or Port 2 list box and
clicking the Configure button. When 7 data bits are selected as default, 00h through 7Fh is transmitted. When 8 data bits
are selected, 00h through FFh is transmitted. Constant values are entered in character or hexadecimal notation into the
source data.
Constant (Character)
Any character available on the computer keyboard can be entered. One character is counted as one byte.
Constant (Hexadecimal)
Use this option to enter the hexadecimal code of any ASCII character. ASCII control codes NUL (00h) through US (1Fh)
can also be entered using this option.
Type
TXD Transmit instruction
RXD Receive instruction
Port
Port 1 Transmit user communication through port 1 (TXD1)
Port 2 Transmit user communication through port 2 (TXD2)
S1 Source 1
Enter the data to transmit in this area.
Transmit data can be constant values (character or hexadecimal), data registers, or BCC.
D1 Destination 1 Transmit completion output can be an output or internal relay.
D2 Destination 2
Transmit status register can be data register D0 through D1298 or D2000 through D7998.
The next data register stores the byte count of transmitted data.
Transmit Data Operand Conversion Type
Transmit Digits
(Bytes)
Repeat BCC Calculation
Calculation
Start Position
Constant 00h-7Fh (FFh) No conversion 1 — — —
Data Register
D0-D1299
D2000-D7999
A: Binary to ASCII
B: BCD to ASCII
–: No conversion
1-4
1-5
1-2
1-99 — —
BCC —
A: Binary to ASCII
–: No conversion
1-2 —
X: XOR
A: ADD
C: Add-2comp
M: Modbus ASCII
M: Modbus RTU
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