Rockwell-automation 1746-BAS BASIC LANGUAGE User Manual download pdf (Page 144)

Publication 1746-RM001A-US-P

11-14 Status Functions

Half-Duplex No Handshaking Modem Control

Half-duplex no handshaking modem control, selected by operational codes 0

through 3, has the following characteristics:

• The RTS output line is activated during transmission, but no RTS On Delay

or RTS Off Delay is performed.

• The DTR output line is not manipulated by the DF1 driver. It is

recommended that you activate DTR in your BASIC program while DF1

communications are taking place

• The CTS and DSR input lines are not monitored nor do they have any affect

on transmissions or receptions.

• A transmission monitor guarantees that transmitter interrupts are being

generated in a timely manner. If a timeout occurs, the DF1_Status is set to

code value 5 if a data packet was being transmitted. Also, RTS is immediately

dropped when this timeout occurs.

Half-duplex without continuous carrier modem control, selected by operational

codes 4 through 7, has the following characteristics:

• The RTS output line is activated only during transmissions. The actual packet

transmission starts after the delay specified by the RTS On Delay parameter,

assuming the CTS input is active by then. When the transmission is complete

and the delay time period specified by the RTS Off Delay parameter has timed

out, RTS is deactivated.

• An actual transmission does not start until the CTS input is active. A

transmission guarantees that transmitter interrupts are being generated in a

timely manner. If a timeout occurs, then the DF1_Status is set to code value 5

if the data packet was being transmitted. RTS is dropped immediately when

this occurs.

• If not already active, the DTR line is raised when the DF1 Driver is enabled.

Even after the DF1 Driver is disabled, it will remain active; the user may

deactivate it via a BASIC Call.

• Characters that are received only are 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.

There is no constant monitoring of DCD even between packets as there is with

the constant carrier selection. Therefore, the DTR line is never deactivated.

IMPORTANT

For proper operation, the Data Carrier Detect (DCD) line from

the modem must be connected to the DSR input of port PRT2.

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Rockwell-automation 1746-BAS BASIC LANGUAGE User Manual Page 144