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

The Process Interrupt feature can be used with groups 0 and/or 1 when they are operatingin either the latched or unlatched mode of operation. In the latched mode, each bitthat is set on in the group remains in that state (regardless of any further change in inputsignal or contact operation) until the group is reset or unlatched. All bits in the group arereset, even if the input signal remains active throughout the execution of the read/resetdigital input register command. In order to again set a bit in the digital input register, apositive transition must occur; for example, the input point must have gone to a 0 value(+0.6V to —52.8V) and then back to a 1 value (+2V to +52.8V) after the digital inputregister was reset. When changing modes, latched to unlatched or unlatched to latched,and the user's input value is in the logical I state, the digital input register indicates alogical 0 until such time as another positive transition takes place.In the unlatched mode of operation, each bit in the group is set on or off dynamicallyas determined by the input signal fluctuations. The output of the digital input registerfollows the user's input value; for example, the user's value at a logical 0 results in alogical 0 output from the digital input register.Exception: The output of the digital input register will not follow the user's inputvalue in unlatched mode whenever a switch from latched mode to unlatched mode takesplace and the user's input value remains in the logical 1 state. Either of two methods canbe used to restore the digital input register to again reflect the user's input values.1. Program the following sequence:—Issue a set-test-signal command (bit 15=0).—Establish a 3-microsecond delay.—Issue a read/reset-digital-input-register command.2. Ensure that the user's input value returns to a logical 0 after the completion oflatched mode operation.Even though the Process Interrupt feature is installed, it can be disabled and enabledunder program control at any time. Program control of the Process Interrupt feature isprovided by the set-digital-input-interrupt-control command.I/O CommandsThe prepare I/O command is used as described in Chapter 4 under "Input/Output Instruction"and in this chapter under "Module Device Addresses." This command applies only togroups 0 and 1 because only these two groups can have the Process Interrupt feature. Theprepare I/O device address field must be 000000 for group 0 or 000100 for group 1.Data transfers between the digital input control and the processor module are accomplishedby immediate read and immediate write commands. The setting of the modifierfield bits in the command further defines the operation to be performed.All read and write I/O commands addressed to the digital input control must use one ofthe following device addresses in order to address the corresponding digital input groupseparately:Device Address000000 0000100 1001000 2001100 3010000 4010100 5011000 6011100 7Digital Input GroupThe module address in the I/O command varies depending upon the physical location ofthe digital I/O module in the 5026 Enclosure.The normal programming routines for digital input are shown in Figures F-3 and F-4 of"Appendix F."IBM 5013 Digital I/O Module Model Al 14-5