Rockwell Automation 1746-BAS BASIC LANGUAGE - Manual (Page 221)

Publication 1746-RM001A-US-P
Input Functions 13-31
If an internal string is chosen, the first character (transaction number) is
incremented upon a successful read transaction to inform the module that new
data is in the string. The value of the transaction number wraps around from 255
to 0.
The DF1 port parameters must be set up with CALL 108. The DF1 port can
operate with full-duplex or half-duplex slave protocol.
Execute CALL 122 once to set up the data transfer parameters. Input and output
image bits (word 0, bit 10) for the slot containing the module, are used to initiate
and notify completion of the transfer. The operation is described below:
1. 1. 1. 1. The SLC processor sets the output file word 0, bit 10 to inform the module
that READ command configured in CALL 122 should be executed.
2. 2. 2. 2. The module issues the appropriate READ command to the PLC. The data
and status are received from the PLC.
3. 3. 3. 3. When data is available, the module transfers the data into the destination
buffer.
4. 4. 4. 4. The module places the transaction status in the input word 1, bits 0-7.
SLC Processor SLC Backplane BASIC or BASIC-T Module
Output File
Word 0, Bit 12
PLC DF1 Network BASIC or BASIC-T Module
DATA FILE
PORT PRT2
READ Command
Data and Status
SLC Processor SLC Backplane BASIC or BASIC-T Module
DESTINATION
BUFFER
SLC Processor SLC Backplane BASIC or BASIC-T Module
Input File
Word 1,
Bits 0 through 7