Rockwell Automation 1746-BAS BASIC LANGUAGE - Manual (Page 146)

Publication 1746-RM001A-US-P
11-16 Status Functions
Full-Duplex With No Handshaking
Full-duplex with no handshaking, selected by operation codes 16 through 23, has
the following characteristics:
•
The RTS output line is activated when the DF1 Driver is enabled and remains
so until the DF1 Driver is disabled.
•
The DTR output line is not manipulated by the DF1 Driver. It is
recommended that the user activate DTR in his/her BASIC program while the
DF1 communications is taking place.
•
The CTS and DSR input lines are not monitored or have any effect on
transmissions.
•
A transmission monitor guarantees that transmitter interrupts are being
generated in a timely manner. If a timeout occurs, then the DF1_Status is sent
to code value 5 if the packet in the process of being transmitted was a data
packet. RTS is not deactivated when this timeout occurs.
Full-Duplex Modem (FDM)
Full-Duplex Modem (FDM), selected by operation codes 24 through 31, has the
following characteristics:
•
The RTS output line is activated when the DF1 Driver is enabled and remains
so until the DF1 Driver is disabled.
•
An actual transmission does not start until the CTS input is active. A
transmission monitor guarantees that transmitter interrupts are being
generated in a timely manner. If a timeout occurs, then the DF1_Status is sent
to code value 5 if the packet in the progress of being transmitted was a data
packet. RTS is not deactivated when this occurs.
•
If DTR is not already active when the DF1 Driver is enabled, it is immediately
activated. It becomes active only if DCD is lost as described in the next
paragraph. Even after the DF1 Driver is disabled, DTR remains active; the user
may deactivate it via a BASIC CALL.
•
For packet receptions, the DCD signal is monitored via the DSR input line. If
DCD is not already active when the DF1 Driver is enabled, then it is
immediately detected when it does go active. At this point, DCD is checked
every 5 ms to make sure it remains active. If it goes inactive, the driver waits 10
seconds for DCD to go active again. If DCD does not go active again in this
amount of time, then the DTR output line is deactivated for a period of time
ranging from 5 to 10 ms in length.
Also, characters that are received are only accepted if the DCD line is active. A
packet reception is aborted if DCD goes inactive during the byte-to-byte
reception of that packet.