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

If a particular amplifier gain was selected by the last convert command, the 16 bitsof data have the format:0 1 15S Data OLill 111111 till••••■••\,■•••••■••■•voar/...•••■,,0•1■■•••■■•■,......,X • XFourteen bits of binary data plus sign (S bit) are returned. The single-bit OL field isset on if an overload condition occurred with the program-selected amplifier gain.The convert portion of the read-and-convert-ADC command converts the analog inputpoint specified by the last convert command, utilizing the same amplifier gain. Thus, ifautomatic gain was specified by the last convert command, then automatic gain is also usedby each subsequent execution of the read-and-convert-ADC command.Since this command performs repetitive operations on a single analog input point, thesolid-state multiplexer is monopolized during this time. To terminate this repetitive readsequence and free the multiplexer, a read-ADC command must be issued if the result of thelast conversion cycle is needed by the program. However, any command other than theread-and-convert-ADC command may be issued to terminate the repetitive read sequence.Read ISW0 5 8 11 16 20 26 31Op code R Fun Zeros Mod DA MA0 0 0 0 1 X XX 0 1 0 0 0 0 0 0 0 0 1 1 1 0 0 1 0 0 XXXXXXtill i i II fill III 11111 111110 8-F 4 0 3 9 0-3 XThis command stores the 16-bit interrupt status word (ISW) associated with the analoginput control into the index register (R), or the accumulator if R=000.Interrupt Status Word (ISW): The 16 bits in the interrupt status word are set byconditions occurring after a convert-analog-input, convert-analog-input-with-externalsynchronization,or read-and-convert-analog-input command is completed, but while thedevice is still busy. Since these errors cannot be indicated to the program by thecondition code, interruptions result from setting on any ISW bit except the busy bit.Setting on any one of bits 3 through 7 also sets on the summary status indicator when theresulting interruption request occurs. After the interruption is accepted, the executionof any command directed to the analog input control resets the ISW.The significant bits in the ISW and their meanings are:Significant Bits Meaning3 Analog-to-digital converter inoperative.5 Invalid analog data. The polarity of the input voltage changed duringthe conversion cycle.7 Overload. The voltage read by the ADC was greater than the inputvoltage range selected by the amplifier.