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

III 1111•1111111111•1111111 III IIIIIIII 11•11 III IIIIIIIIIIIIIIII 111•I11111111111111111.7FUNCTIONAL DESCRIPTIONThe 5024 can attach to the 5010E processor mounted in a 5026, A2, C3, or C6 enclosures.Any one of the three model configurations can be attached. The 5024 communicates withthe System/7 through control logic in the 5010E processor. The System/7 communicateswith the 5024 through set interrupt commands. The data words selected by the commandsdirect the 5024 to initiate I/O operations or reset operations. The actual command tobe performed by the 5024 is located in an area of storage called the Input OutputTransfer Block (IOTB). The IOTB also contains other parameters that are used duringthe I/O operation. Once the initiate I/O has been issued, cycle steal operations areused to accomplish data transfer. Depending on the I/O device selected (either the2502 or Printer), the IOTB specifies the appropriate status buffer starting addressthat has been set up for each device. The data controller fills the specified statusbuffer at the end of the cycle steal operation.S/7 50245010E processorContr0IIerReaderattachmentPrinterattachment2502PrinterData ControllerAll control logic for the 5024 is in the data controller. A single System/7 XIOinstruction (initiate I/O) initiates a series of cycle steal sequences that areterminated with an interrupt from the 5024. The data controller accesses storagelocation 0008 for the address of the I/O Transfer Block (IOTB) which specifiescommands and control information for the 5024.I/O Transfer BlockFigure 17-4 shows the format of the IOTB and status buffer. The IOTB is a five wordblock that contains information set up by the user's program to control data transferbetween the System/7 and the 5024. A typical data transfer between the System/7 and adevice in the 5024 is as follows:1. The IOTB is established by user program in any available main storage location.2. Location 0008 is initialized by user program with the address of the IOTB.3. User's program issues initiate I/O command.4. The controller cycle steals address from location 0008.5. The controller cycle steals each word of the IOTB and determines the command,device to be selected (printer or card reader), data starting address, and wordcount.6. The controller performs the data transfer between main storage and the selecteddevice via cycle steal.7. The controller transfers device information to the status buffer in main storage.8. The controller interrupts System/7 to indicate that operation is complete, and the5024 is ready for the next transfer.9. The user program examines status buffer for ending conditions.10. The user program clears status buffer.17-4 GA34-0003