S80296SA datasheet(13/40 Pages) INTEL

13 / 40 page

PRELIMINARY

80296SA COMMERCIAL CHMOS 16-BIT MICROCONTROLLER

NMI

Nonmaskable Interrupt

In normal operating mode, a rising edge on NMI generates a nonmaskable interrupt.

NMI has the highest priority of all interrupts except trap and unimplemented opcode.

Assert NMI for greater than one state time to guarantee that it is recognized.

If NMI is held high during and immediately following reset, the microcontroller will

execute the NMI interrupt service routine when code execution begins. To prevent

an inadvertent NMI interrupt vector, the first instruction (at F2080H) must clear the

NMI pending interrupt bit.

ANDB INT_PEND1, #7FH.

During idle mode, a rising edge on NMI causes the microcontroller to exit idle mode

and branch to the interrupt service routine.

ONCE

On-circuit Emulation

Holding ONCE high during the rising edge of RESET# places the microcontroller

into on-circuit emulation (ONCE) mode. This mode puts all pins, except READY,

RESET#, ONCE, and NMI, into a high-impedance state, thereby isolating the

microcontroller from other components in the system. The value of ONCE is latched

when the RESET# pin goes inactive. While the microcontroller is in ONCE mode,

you can debug the system using a clip-on emulator.

To exit ONCE mode, reset the microcontroller by pulling the RESET# signal low. To

prevent inadvertent entry into ONCE mode, connect the ONCE pin to V

SS.

P1.7:0

I/O

Port 1

This is a standard, 8-bit, bidirectional port that shares package pins with individually

selectable special-function signals.

Port 1 shares package pins with the following signals: P1.0/EPA0, P1.1/EPA1,

P1.2/EPA2, P1.3/EPA3, P1.4/T1CLK, P1.5/T1DIR, P1.6/T2CLK, and P1.7/T2DIR.

P2.7:0

I/O

Port 2

This is a standard, 8-bit, bidirectional port that shares package pins with individually

selectable special-function signals.

Port 2 shares package pins with the following signals: P2.0/TXD, P2.1/RXD,

P2.2/EXTINT0, P2.3/BREQ#, P2.4/EXTINT1, P2.5/HOLD#, P2.6/HLDA#, and

P2.7/CLKOUT.

P3.7:0

I/O

Port 3

This is a standard, 8-bit, bidirectional port that shares package pins with individually

selectable special-function signals.

Port 3 shares package pins with the following signals: P3.0/CS0#, P3.1/CS1#,

P3.2/CS2#, P3.3/CS3#, P3.4/CS4#, P3.5/CS5#, P3.6/EXTINT2, and

P3.7/EXTINT3.

P4.3:0

I/O

Port 4

Port 4 is a standard, 4-bit, bidirectional I/O port with high-current drive capability.

Port 4 shares package pins with the following signals: P4.0/PWM0, P4.1/PWM1,

and P4.2/PWM2. P4.3 has a dedicated package pin.

Table 4. Signal Descriptions (Continued)

Name

Type

Description

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