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

Page of GA34-0003-6, -7As Updated August 20, 1976By TNL GN34-0340Register Bits (ON status)0 Bit advance to the bit counter, clocks, shift register, etc. is active.1 IPL mode. Set on by xmit IPL and stays on as long as the adapter is in IPL mode.2 IPL start is sent to the CPU.3 A SYN character has just been decoded.4 An ACKO, WACK, or RVI has just been decoded.5 A DLE has just been decoded.6 Terminal address has been properly received (multipoint only).7 Adapter in ASCII mode. If this bit is off, the adapter is in EBCDIC mode.8 Status of the serial receive data line.9 Character phase is active.10 Accum BCC is active.11 Bit time 7 is active.12 Transparent mode is active.13 Data transfer mode is active.14 MST clear to send is active.15 Reserved.Read Residual Address0 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 1 1 1 0 0 1 1 0 0 0 0 0 0 0 0I I I I II 1 1 1 1 1 1 III 1 1 1 1 1 1 1 1 1 10 8-F 4 0 F 3 0 0This command stores the contents of the BSCA's storage address register (which is usedduring BSCA cycle steal operations and is updated by the BSCA) in the register specifiedby the R field, or the accumulator if R=000. Its purpose is to allow the program todetermine the exact point during data transfer at which a subchannel error or exceptioncondition occurred. This command does not cause an interruption. The storage addressregister in the BSCA is not reset by this command or by a reset I/O command; it is resetonly by a power-on reset. Depending on the time the storage address register is read, itcontains either the address of the next DCB to be used (in a chaining operation); theaddress of one of the words in a DCB; or the address used for data transfer.INITIAL PROGRAM LOAD (IPL)The host system determines when to initiate an IPL to the System/7 through the BSCA.The IPL is accepted only when the host attach switch on the System/7 console is in theENABLE and IPL position. In a multipoint configuration, the BSCA maintains bytesynchronization and searches for its assigned address character. When it is detected,followed by a second address character and the IPL sequence (DC1 DC1) ENQ, theadapter responds with an acknowledgement (ACKO) and enters the selected mode. Ina point-to-point switched network IPL sequence, the address characters are not necessary.The host system then transmits DLE STX, to put the BSCA into transparent text mode,followed by the IPL program. The program is placed in System/7 storage starting ataddress 0000.8-12 GA34-0003