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

11111 1 11•1111111111111111111111 1 111111.11111111111111111 111111111111111111111 1 1111 111•1111111111111111111111MrIOTB WordsThe five IOTB words are described as follows:Word 1-Command Word. The first four bits of this word contain the command to beexecuted by the controller. The last eight bits contain carriage control information.Carriage control applies to operation of the printer when the output print command isissued. For further definition of carriage control see the command word under Printer.Word 2—Printer Status Address. The address of a five word status buffer for thePrinter.Word 3-2502 Status Address. The address of a five word status buffer for the2502.Word 4—Word Count. The number of words to be transferred during the operation. Theoutput diagnostic/initialize controller, input diagnostic, and output print line commandsrequire the user to set a valid word count. The controller establishes the word count forall other commands.Word 5—Data Address. The address of the buffer in the System/7 into which datawill be stored or transferred.Status BuffersThe Status Buffer is a five word block in main storage allocated by the user programand filled by the controller with status and control information. The Printer and 2502each have a status buffer. Words 1 through 4 are stored on a normal interrupt. Word 5 isstored on an attention interrupt.Word 1 and Word 2. These status words are explained in the 2502 and Printersections of this chapter under "Status Buffers."Word 3—Residual Address. The last System/7 address accessed by the controller ina command sequence.Word 4—Normal Interrupt Indicator. Bit 0 of this word is set to 1 by thecontroller to indicate that a command sequence ending interrupt has occurred for thecorresponding I/O device. This word must be read and set to zero by the System/7program when it services an interrupt from the 5024. Bits 1 through 15 are set to zeroby the controller.Word 5—Attention Interrupt Indicator. An interrupt will be generated and bit 0of this word is set to 1 when the associated I/O device goes from a not ready state toa ready condition. Bits 1 through 15 are set to zero by the controller. Status bufferwords 1, 2, 3, and 4 are not changed by an attention interrupt. The program must readthis word and set it to zero when servicing an interrupt from the 5024.