Intel 80C196NU Modifying Interrupt Priorities, INTMASK1, NMI EXTINT3 EXTINT2, EPA3 EPA2 EPA1

Models: Microcontroller 80C196NU 8XC196NP

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STANDARD AND PTS INTERRUPTS

INT_MASK1

Address:

0013H

 

Reset State:

00H

The interrupt mask 1 (INT_MASK1) register enables or disables (masks) individual interrupt requests. (The EI and DI instructions enable and disable servicing of all maskable interrupts.) INT_MASK1 can be read from or written to as a byte register. PUSHA saves this register on the stack and POPA restores it.

7

NMI

EXTINT3

EXTINT2

OVR2_3

 

 

 

 

0

OVR0_1

EPA3

EPA2

EPA1

 

 

 

 

Bit

 

Function

 

Number

 

 

 

 

 

 

 

 

7:0

Setting a bit enables the corresponding interrupt.

 

 

The standard interrupt vector locations are as follows:

 

 

Bit Mnemonic

Interrupt

Standard Vector

 

NMI

Nonmaskable Interrupt

FF203EH

 

EXTINT3

EXTINT3 pin

FF203CH

 

EXTINT2

EXTINT2 pin

FF203AH

 

OVR2_3

EPA Capture Channel 2 or 3 Overrun

FF2038H

 

OVR0_1

EPA Capture Channel 0 or 1 Overrun

FF2036H

 

EPA3

EPA Capture/Compare Channel 3

FF2034H

 

EPA2

EPA Capture/Compare Channel 2

FF2032H

 

EPA1

EPA Capture/Compare Channel 1

FF2030H

 

An overrun on the EPA capture/compare channels can generate the multiplexed

 

capture overrun interrupts. The EPA_MASK and EPA_PEND registers decode these

 

multiplexed interrupts. Write to EPA_MASK to enable the interrupt sources; read

 

EPA_PEND to determine which source caused the interrupt.

 

 

 

 

 

Figure 6-6. Interrupt Mask 1 (INT_MASK1) Register

6.5.2Modifying Interrupt Priorities

Your software can modify the default priorities of maskable interrupts by controlling the interrupt mask registers (INT_MASK and INT_MASK1). For example, you can specify which interrupts, if any, can interrupt an interrupt service routine. The following code shows one way to prevent all interrupts, except EXTINT3 (priority 14), from interrupting an SIO receive interrupt service routine (priority 06).

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Intel 80C196NU, 8XC196NP, Microcontroller Modifying Interrupt Priorities, INTMASK1, NMI EXTINT3 EXTINT2, EPA3 EPA2 EPA1