Black Box PCW22A-R4 manual Presentation of Data from A/S-2G to Synchronous Device, Line Turnaround

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CHAPTER 4: Operation

If SW3, Switch #7 is OFF, the A/S-2G will send an X-OFF (ASCII DC3, 13 Hex) to the asynchronous device when RAM reaches a nearly-full state. This prevents data from being lost due to a buffer overrun. When RAM space is available, the A/S-2G will send an X-ON (ASCII DC1, 11 Hex) to resume transmission.

Alternatively, if SW3, Switch #7 is ON, the A/S-2G will lower the DTR (Pin 20) when RAM reaches a nearly-full state. When RAM space is available, the A/S-2G will again raise DTR to resume transmission.

4.1.7 PRESENTATION OF DATA FROM A/S-2G TO SYNCHRONOUS DEVICE

When an asynchronous device begins transmission to the A/S-2G and the A/S-2G has enough data for a block, the A/S-2G bids for the synchronous line and proceeds in standard bisynchronous protocol. See the Data Flow Diagrams on pages 15 through 19.

NOTE

Bracketed sections indicate a selectable option. Arrows indicate the direction of data flow.

4.1.8 VERIFICATION OF DATA RECEPTION

When operating in full duplex mode from the asynchronous side, SW3, Switches #1 and #2 permit visual assurance of accurate and complete transmission. When SW3, Switch #1 is ON, the A/S-2G will immediately echo back all the data it receives from the asynchronous device. When SW3, Switch #2 is ON, the A/S-2G will send a CR, LF, and EOT to the asynchronous device after a complete transmission and a line turn-around have successfully been completed.

4.1.9 LINE TURNAROUND

The final record transmitted from the asynchronous side must be terminated with a “Control D” (ASCII 04 Hex) character. This notifies the A/S-2G that the asynchronous device has completed its entry and is relinquishing the line. After all data is sent, the A/S-2G will send an EOT sequence to the synchronous side.

Data Flow — A/S-2G to Synchronous Device

Bisynchronous Device

A/S-2G Converter

Asynchronous Device

Characters up to maximum BSC Block size (2770, 2780, 3780) or one 128 character record (3741) terminated by CR (0D Hex) = Block A of data received in start/stop format

(Echo all but CR LF)

ENQ

Line Bid

AA AA 32 32 32 32 2D FF FF

ACK 0

Positive Acknowledgment—

Even AA AA 32 32 32 32 10

70 FF FF

Send block A

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Contents Protocol Converter FCC Statement Protocol Converter A/S-2G Table of Contents Synchronous Device to Asynchronous Device Specifications RXCIntroduction Installation Unpacking and InspectionData Flow Control 2 SW2 Switch #4 on = SELF-DIAGNOSTICSData Terminal Ready DTR Signal Options Reconfigure Switch ModeReset Options 5 RS-232 PASS-THROUGH OptionsClear to Send CTS Signal Options Baud Rate OptionsModem or DIRECT-TO-TERMINAL Connection Preparing the A/S-2G for Connection to a Synchronous Device Carrier OptionsCable Requirement External or Internal Clocking Option Command PASS-THRU Operation Asynchronous Device to Synchronous DeviceUSE of Carriage Return a 2770/2780 Mode Flow ControlPresentation of Data from A/S-2G to Synchronous Device Verification of Data ReceptionLine Turnaround Data Flow A/S-2G to Synchronous Device NAK Echo CR LF Send block F Echo all but CR LF Data Flow A/S-2G to Synchronous Device Synchronous Device to Asynchronous Device Synchronous Input Data FormatEbcdic characters stripped Data Flow A/S-2G to Asynchronous Device Operation EOT Transparency Mode of Operation Installing or Replacing PromsConversions and Connections RS-232 Cable Chart GNDCode Conversions Special Conversions Printed Circuit Board Layout Printed Board Circuit LayoutPark Drive Lawrence, PA
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