IBM System/7 Functional Characteristics - All about the IBM 1130 ...

Bits Meaning4* No COD character. No turnaround character or sequence has been decodedby the BSCA, the word count has been decremented to zero, and the chainingflag is off. An EOT or NAK must be received with at least 4 contiguousone-bits following it to be valid.5 Diagnostic mode. This bit is set on when the BSCA is in diagnostic mode dueto a write diagnostic control command.6 Data set ready. The modem has returned data set ready in response to dataterminal ready to indicate the "off hook" condition during an auto answeroperation. This bit is not reset by a read ISW command. Data set ready causesan interrupt only when the data set becomes ready in response to an enableoperation and the chaining flag is off.7* Data set error. While in a transmit or receive mode the data set ready linefrom the modem has dropped with data terminal ready on, or the clear tosend line from the modem has dropped with request to send on.8* Storage data check. The storage location accessed by the BSCA during thecurrent instruction contains a parity error. The oepration is terminated andthe data is not transmitted over the data link. The storage address register isnot incremented.9* Program check. The main storage address presented by the BSCA during thecurrent input/output operation for data, or DCB address, exceeds the storagesize installed in the system. The operation is terminated. (An address ofFFFD, FFFE, or FFFF presented as a DCB address does not cause a programcheck when the DCB is fetched.)10 Reserved.11 Channel end. This bit is set on at the termination of a subchannel busycondition. The busy condition exists from the initialization of a successfulinitiate I/O command to the point where the count goes to zero and the DCBchaining flag is off; a COD is detected with the chaining flag off; or an erroror exception condition occurs.Channel end is not itself an error indicator; however, it is set on if any errorterminates any subchannel operation. The BSCA does not separate channelendinterruptions from device-end interruptions.12 Busy, This bit is set on when the BSCA accepts a data transfer operation andis ready to fetch the DCB, or the BSCA is given a disable terminal operation.It is not an error condition; it indicates that the BSCA is in the working state.Busy is reset when device end is set. Busy does not cause an interruptionrequest.13 Device end. This bit is set on whenever any operation is terminated, forwhatever reason. It is not itself an error condition.14* Interface data check (BCC Error). The BCC received over the data link doesnot compare with the BCC accumulated. Also, LRC or VRC error in ASCIImode.15 Multipoint. The BSCA is being used as a tributary in a multipoint configuration.*The summary status bit is also set along with this bit.Read ISW Extension (for diagnostic use only)0 5 8 11 16 20 26 31Op code R Fun Zeros Mod DA MA0 0 0 0 1 XXX 0 1 0 0 0 0 0 0 1 0 1 1 0 0 1 1 0 0 0 0 0 0 0 0I 1 I I II II I 1 1 1 I I 1 1 1 1 1 1 1 I0 8-F 4 0 B 3 0 0This command transfers 16 bits of BSCA status information for diagnostic use to theregister specified by the R field, or the accumulator if R=000.Binary Synchronous Communications Adapter 8-11