Rockwell Automation 1746-BAS BASIC LANGUAGE - Manual (Page 142)

Publication 1746-RM001A-US-P
11-12 Status Functions
CALL 108 – Enable DF1
Driver Communications Purpose
Use CALL 108 to enable DF1 driver communications via port PRT2.
This routine has six input arguments and no output arguments. The first input
argument specifies the operational code selection that indicates the mode of
operation for the DF1 driver. The operational code specifies the following DF1
parameters:
•
full-duplex or half-duplex slave operation
•
duplicate packet detection (DPD) selection
•
BCC or CRC error checking selection
•
enable embedded responses (ER) or auto-detect embedded responses (ADER).
If ADER is selected, enabled responses are not transmitted until an embedded
response is received. It is assumed that if the device being communicated with
can send an ER it can also receive them (only applies to full-duplex operation).
•
modem handshaking selection:
– half-duplex options:
•
No HandShaking (NHS)
•
Half-Duplex Modem without Continuous Carrier (HDMwoCC)
•
Half-Duplex Modem with Continuous Carrier (HDMwCC)
– full-duplex options:
•
No HandShaking (NHS)
•
Full-Duplex Modem (FDM)
Legal values for the operational code are 0 to 11 for half-duplex mode and 16 to 31
for full-duplex mode. Table 11.B lists the legal values for the half-duplex
operational codes and their corresponding mode of operation. Table 11.C lists the
legal values for the full-duplex operational codes and their corresponding mode of
operation.
A special range of operational codes (32 - 43) are also accepted. These codes are
identical to codes 0 - 11 except that the end of transmission (EOT) packets are
suppressed. This operation is a deviation from the standard DF1 protocol and
should only be used where transmissions from a slave module are minimized.
When using one of these selections, the DF1 driver does not respond to ENQuires
from a DF1 master unless there is a data packet transmitted.
IMPORTANT
DF1 can only be enabled if jumper JW4 on the module is in the
correct position. Refer to the SLC 500™ BASIC and BASIC-T
Modules User Manual (publication number
1746-UM004A-US-P) for additional information.