Overview

The BISYNC key acts as an interface between a DEVICE key and a using program. It provides some of the logic necessary to run a BISYNC interface.

IBM Bisync operates in two general modes; point-to-point and multi-drop. The initial handshakes differ between the two as follows:

In point to point, when a station has something to send it bids for the line by sending an ENQ and waiting for an ACK-0 response.

In multi-drop, one station is the "controlling" station and all the others are "tributary" stations. The controlling station is responsible for polling the tributaries for any transmissions they may have and selecting them when there is traffic for them. All traffic goes through the controlling station.

After the initial protocol has determined which station is to send and which is to receive, data transmission proceeds by sending blocks of data. These blocks can be sent either in transparent mode (all 256 byte patterns valid), or in non-transparent mode (some patterns reserved for link control). The receiving station acknowleges each block with an alternating ACK-1/ACK-0 sequence. The receiving station may NAK a block in error (which must be re-transmitted), WACK a block it is not yet ready to receive, or send a RVI to interrupt the sender.

The transmission is ended with EOT.

It might be desirable to have an operation that is used by a tributary station to automatically respond EOT (nothing to send) to a polling sequence. This operation would end upon receipt of a selection sequence, error or a halt signal from the caller (see below).

An application may desire to halt both the prepare-read operation and the operation described above before they have reached their natural end. An additional domain could provide this service, or the application could call the device key directly. I (WSF) currently lean toward the extra domain. Its key would be returned on the factory call.

Additional calls could be defined to:

Continue a poll/delay (via KIWAIT) loop until a tributary responded with traffic or HIO.

Automatically recover from certain errors. e.g. Check the ACK-0/1 sequence on write operation and deliver ACK-0/1s on reads.

Send a file using 2780/3780/HASP protocol.

etc.

BISYNCF(0;PSB,M,SB,DEVICE==>c;BISYNC) - Create BISYNC driver
.(ACB) - This should be compatible with the Device Allocator <devaloc> which means that you must define a receptionist function. The tape system or the Series/1 device driver are two different examples of how this has been done in the past.

.(ACB) - BISYNC could accept two calls (at the same time). BISYNC(cancel_operation ==>) would cancel a prepare/read (etc). This implementation is not dissimilar to the X.25 Circuit Key which accepts both a read and a write. An extra domain is not needed as only the RESUME key needs to be stashed away while waiting for the Prepare/read to complete or the cancel call.

PSB is a prompt space bank, M is a meter, SB is a space bank and DEVICE is a device I/O key to a hardware BISYNC control unit.

c=0 - BISYNC is a key to a new BISYNC device driver which communicates through device DEVICE.

c=1,2 - As from the factory

c=3 = DEVICE is not an acceptable key or its device is not acceptable.

BISYNC(0;==>c(2,sense)) - Wait for connection
c=0 - Connection complete, sense is X'0000'

c=2 - Unit check (Enable timeout), no connection exists, sense is the data returned by the device key.

BISYNC(1,number==>c,(2,sense)) - Dial
number is the telephone number to be dialed plus any required controls (i.e. EON=X'0C' or SEP=X'0D')

c=0 - Connection complete, sense is X'0000'

c=2 - Unit check, sense is the sense data returned by the device key.

BISYNC(2==>c,(2,sense)) - Disable
c=0 - Connection dropped, sense is X'0000'

c=2 - Unit check (Modem timeout on disable), sense is the sense data returned by the device key.

BISYNC(3,mode==>c) - Set Mode
mode is X'40' for EIB mode on or X'00' for EIB mode off.

c=0 - Mode set complete

c=kt+3 - mode is not 0 or X'40'

BISYNC(4==>c,data) - Read line
c=0 - No errors occured, data is data read from line

c=1 - Unit Exception (i.e. EOT received).

c=2 - Unit check, data is (2,sense data from device key), (n,data from line).

BISYNC(5==>c,data) - Prepare and then Read line
Issues a prepare CCW to wait for character phase chained to a read CCW. The prepare CCW does not time out.

c=0 - No errors occured, data is data read from line

c=1 - Unit Exception (i.e. EOT received).

c=2 - Unit check on prepare CCW, data is (2,sense data from device key).

c=3 - Unit check on read CCW, data is (2,sense data from device key), (n,data from line).

BISYNC(6,data==>c,sense) - Write line
Data is sent to the line.

c=0 - No errors occured, sense is X'0000'.

c=1 - Unit Exception (i.e. EOT received), sense is X'0000'.

c=2 - Unit check, sense is (2,sense data from device key).

BISYNC(7,data==>c,sense) - Transparent write line
From data, (n-2,data) is sent to the line with one write CCW. The last two bytes of data are sent with a separate, command chained, CCW.

c=0 - No errors occured, sense is X'0000'.

c=1 - Unit Exception (i.e. EOT received), sense is X'0000'.

c=2 - Unit check, sense is (2,sense data from device key).

c=kt+3 - Data doesn't start with a DLE/STX or is less than 4 bytes long.

BISYNC(8,data==>c,data2) - Write line then read
Data is sent to the line. A read CCW is command chained to the write CCW.

c=0 - No errors occured, data2 is the data returned by the read CCW.

c=1 - Unit Exception (i.e. EOT received), data2 is the data returned by the read CCW.

c=2 - Unit check on write CCW, data2 is (2,sense data from device key).

c=3 - Unit check on read CCW, data2 is (2,sense data from device key), (n,data from read CCW).

BISYNC(9,data==>c,data2) - Transparent write line then read
From data (n-2,data) is sent to the line with one write CCW. The last two bytes of data are sent with a separate, command chained, CCW. A read CCW is command chained from the second write CCW.

c=0 - No errors occured, data2 is the data returned by the read CCW.

c=1 - Unit Exception (i.e. EOT received), data2 is the data returned by the read CCW.

c=2 - Unit check on one of the write CCWs, data2 is (2,sense data from device key).

c=3 - Unit check on read CCW, data2 is (2,sense data from device key), (n,data from read CCW).

c=kt+3 - Data doesn't start with a DLE/STX or is less than 4 bytes long.

BISYNC(10,polldata==>c,data) - Poll and then read
Polldata is sent to the line with a Poll CCW. It consists of n(max 7 character station addressENQ<index>)EOT. A read CCW is command chained to the poll CCW.

c=0 - Successful poll, data is the data returned by the read CCW and consists of the <index> from the polldata followed by the data returned from the remote station.

c=1 - Poll list complete, no station has anything to send.

c=2 - Unit check on poll CCW, data is (2,sense data from device key).

c=3 - Unit check on read CCW, data is (2,sense data from device key), (n,data from read CCW).

c=kt+3 - Polldata doesn't end with an EOT.

BISYNC(11==>c,data) - Address prepare then read
A command chained address prepare CCW followed by two read CCWs is started.

c=0 - Unit was selected, data is the data returned by the first read CCW.

c=1 - Unit was polled, data is the data returned by the second read CCW. (i.e. The Address prepare CCW ended with Status Modifier.)

c=2 - Unit check on address prepare CCW, data is (2,sense data from device key).

c=3 - Unit check on first read CCW, data is (2,sense data from device key), (n,data from first read CCW).

c=4 - Unit check on second read CCW, data is (2,sense data from device key), (n,data from second read CCW).