Program Logic Manual - All about the IBM 1130 Computing System

Acknowledge and Receive. If the operation is anAcknowledge and Receive, SCAT11. puts the addresses of the read response, writeresponse, and timeout routines for the Receiveoperation into the interrupt branch addresses2. determines the type of acknowledgement to betransmitted from digit 2 of the control parameter(digit 2 zero indicates a positive acknowledgement,non-zero indicates a negative acknowledgment)3. performs a Start Write (puts the SCA in thetransmit mode and causes a write responseinterrupt)4. sets the retry counter to 75. sets RTBSY on (non-zero)0, returns to the calling routine at LIBF+4ErrorsWhen SCAT1 detects an error in the calling processing,a code indicating the error found is placed inthe accumulator, the address of the LIBF is placedinto location 40 in COMMA, and a branch is takento location 41, a WAIT. When PROGRAM STARTis pressed, a branch is taken to the address inlocation 40 (i.e. , the LIBF is re-executed).Interrupt ProcessingThe interrupt processing routine• Handles read response, write response, andtimeout interrupts for the Open, Transmit, andReceive operations• Handles the auto answer request interrupt• Maintains an error statistics log of certain error• Is able to log timeouts and all characters transmittedand receivedOperationThe paragraphs below describe the processing performedby SCAT1 to accomplish an entire operation(Open-Data In, Open-Data Out, Transmit, orAcknowledge and Receive). Actually, this processingis accomplished in a series of interrupts initiated bythe user's call to SCAT1.An interrupt occurs for each character receivedor transmitted. SCAT1, by means of programmedindicators, keeps track of the characters to bereceived or transmitted next. After transmissionor reception of each character, SCAT1 returns tothe interrupted program.At the completion of an entire operation, a turnaroundof the line occurs and IDLE characters aretransmitted for 1.5 seconds. During this 1.5seconds the user must call SCAT1, specifying thenext operation to be performed.When entered from ILSO1 due to an interrupt bythe SCA, SCAT1 senses the device status word todetermine the type of interrupt.Write Response Interrupt. If a write responseinterrupt has occurred, SCAT11. branches to the write response routine pointedto by the interrupt response addresses as setup in the call processingRead Response Interrupt. If a read responseinterrupt has occurred, SCAT11. checks to determine if a simultaneous timeoutinterrupt has occurred2. branches to the timeout routine pointed to bythe interrupt response addresses as set up inthe call processing if a simultaneous timeoutinterrupt has occurred3. reads the character received by the SCA intocore storage if no simultaneous timeoutinterrupt has occurred4. branches to the read response routine pointedto by the interrupt response addresses as §etup in the call processingTimeout Interrupt. If a timeout interrupt has occurred,SCAT11. branches to the timeout routine pointed to by theinterrupt response addresses as set by thecall processingAuto Answer Interrupt. If an auto answer interrupthas occurred, SCAT11. determines from bit 6 of the DSW if the autoanswer interrupt is disabled/enabled (bit 6zero indicates disabled, 1 enabled)2. returns to ILSO1 if the auto answer interruptis disabled3. stores a non-zero value at the I/O area addressif the auto answer interrupt is enabled4. disables the auto answer interrupt5. returns to ILSO1Write Response (Open). If the mode of operationis Data In, the write response routine1. transmits the End of Idle sequence2. performs a Start Read (puts the SCA in the1 08. 1