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

For a single-character transmission, the transmit character command can be used withouta preceding transmit control command. In this case, however, only a device-end interruptionrequest occurs (ISW bit 13 set), and no ready-to-transmit interruption requestresults from the single transmit character command. After a single-character message istransmitted in this manner, the ACCA returns to standby mode.Read Character0 5 8 11 16 20 26 31Op code R Fun Zeros Mod DA MA0 0 0 0 1 X X X 0 1 0 0 0 0 0 0 1 0 0 0 0 0 1 1 0 0 0 0 0 0 0 01 11 II II 1 11 III 11 I 11 III 110 8-F 4 0 8 3 0 0This command stores the character received from the host processor into bits 8 to 15 ofthe index register (R), or the accumulator if R=000. If the ACCA is in transmit mode, itreturns condition code 1 to the processor and sets bit 4 (ACCA check) in the direct controlchannel status word.Bits 0 to 7 of the register or accumulator contain 0 if the ACCA is not operating inbinary data mode. If the ACCA is operating in binary data mode, the read charactercommand stores a 16-bit data word in the index register or accumulator.The read character command is normally issued following a character-received interruptionrequest from the ACCA.Reset ACCA0 5 8 11 16 20 26 31Op code R Fun Zeros Mod DA MA0 0 0 0 1 * * * 0 0 1 0 0 0 0 0 1 0 0 0 0 0 1 1 0 0 0 0 0 0 0 0MI II II 1111 III 111 II II III0 8 2 0 8 3 0 0This command performs a halt I/O function in the ACCA. Any pending interruption,device status, and all other controls are reset, with the single exception of data sent by aprepare I/O command. The R field in the command is ignored.Following this reset command, the ACCA is in the standby mode of operation ifinterruptions are allowed, and the host attachment switch is in the enable or enable andIPL position. Incoming messages can be received, or transmit operations can begin, undercontrol of a System/7 program. If interruptions are prevented, an IPL sequence will stillbe recognized when the ACCA is reset to standby mode. (See "Initial Program Load (IPL)"in this chapter.)Asynchronous Communications Control Attachment 7-9