operation on two signed numbers is too large to be represented or memory

Operation on two signed numbers is too large to be

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operation on two signed numbers is too large to be represented or memory location The 8086 will get the CS value for the start of the type 4 interrupt service procedure from address 00012H and the IP value for the start of the procedure from address 00010H It is useful to detect overflow error in signed arithmetic operations There are two ways to detect and respond to an overflow error in a program Put the jump if overflow instruction (JO) immediately after the arithmetic instruction Put the interrupt on overflow instruction (INTO) immediately after the arithmetic instruction CSE – 341 : Microprocessors BRAC University
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Summary of 8086 Interrupt Function … 21 What happens if two or more interrupts occur at the same time? Higher priority interrupts will be served first Interrupt Type Priority DIVIDE ERROR, INTn, INT0 NMI INTR SINGLE STEP HIGHEST LOWEST CSE – 341 : Microprocessors BRAC University
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22 The 8259A Priority Interrupt Controller Adds 8 vectored priority encoded interrupts to the microprocessor Can be expanded without additional hardware to accept up to 64 IRQ (one 8259A master, and one slave) D0-D7: Bidirectional data connections IR0-IR7: Interrupt request inputs WR΄: Write input strobe RD΄: Read input connects to the IORC INT: Output, connects to μP INTR pin INTA΄: Input, connects to μP INTA΄ pin A0: Command word select CS΄: Chip select input SP/EN΄: Slave program/enable buffer pin CAS0-CAS2: Outputs from master to slave for cascading multiple 8259A chips CSE – 341 : Microprocessors BRAC University
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23 Connecting a single 8259A controller CSE – 341 : Microprocessors BRAC University
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8259A Internal block diagram 24 CSE – 341 : Microprocessors BRAC University
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The 8259A System Connections 25 The 8259A is used to increase the number of interrupts The 8 bit data bus allows 8086 to send control words to the 8259A and read a status word from the 8259A and also allows to send interrupt types to the 8086 The RD’ and WR’ inputs control the transfer When an interrupt occurs corresponding bit becomes 1 in (IR0-IR7), it checks IRR to know which interrupt has occurred, it checks IMR to know which interrupts are masked and it checks ISR to know which interrupts are in service If the interrupt occurs is in higher priority, not masked and its in higher priority than the interrupt which was in service then its validate and it will be send to the µp on INTR CSE – 341 : Microprocessors BRAC University
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26 Example - 82C55 Keyboard Interrupt Circuit CSE – 341 : Microprocessors BRAC University
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  • Spring '17
  • Dr. Jia uddin
  • Interrupt, BRAC University

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