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

INPUT/OUTPUT INSTRUCTIONOne instruction operation code services I/O devices. Function bits in the input/outputinstruction determine which one of the following basic I/O commands is performed:1. Immediate Write. Sends one word of data from a processor register to an I/O device.2. Immediate Read. Receives one word of data from an I/O device and places the datainto a processor register.3. Prepare I/O. Sends one word of interruption control information from a processorregister to an I/O device.4. Halt I/O. Resets an I/O device.5. Set Interrupt. Sends one word of data to establish an interruption request, eitheron a priority level or to a host processor.6. Read Cycle Steal. Sends up to 3,072 words of data from the disk storage moduleto main storage.7. Write Cycle Steal. Sends up to 3,072 words of data from main storage to the diskstorage module.Execute I/O (P10 or X10)0 5 8 11 16 20 26 31Op code Fun Zeros Mod DA MA0 0 0 0 1 X X X XXX 0 0 0 0 0 XXXX XXX X. XXXXXXI III I I 1111 1 11111 11111,■aw...,.e.a.."•■,....w..",.nII..,.e..n.A■••••*v•■••••ot■nml••Nflir•••••■••••.„,••■.,••••••y.■,•■••■■,,■Iwe0 8-F X 0 X X 0-3 XOne of the seven basic input/output commands is performed, using an index register(or the accumulator if R=000) if data or control information is needed.The function (Fun) field (bits 8 to 10) determines the type of I/O operation to beperformed. Valid values and their meanings are:001—Immediate write010—Immediate read011—Prepare I/O100—Halt I/O101—Set interrupt110—Read cycle steal111—Write cycle stealA function field value of 000 causes a program check interruption on processor modulemodels A and B. The seven valid I/O operations are discussed in greater detail under"I/O Command Functions."Bits 11 to 15 of the PIO instruction are not used, but their values must be set to 0.The modifier field, bits 16 to 19 (bits 0 to 3 of the second instruction word), is usedonly with the read or write function code. These modifier bits further define the read orwrite operation to be performed. The contents of the modifier field are indicated in theformat of each specific I/O command when the command is described for an I/O deviceor module.The device address field, bits 20 to 25 (bits 4 to 9 of the second instruction word),specifies a point, group, or device within a module. Bits 20 to 23 contain a 4-bitsubaddress; bits 24 and 25 are reserved and must be set to 0. The assigned deviceaddresses are discussed separately for each module.The module address field, bits 26 to 31 (bits 10 to 15 of the second instruction word),selects the 5026 Enclosure and the I/O module location being addressed by the PIOinstruction as shown in Figure 4-3.Processor Instructions 4-55