AM186EM-33VCSLASHW datasheet(33/98 Pages) AMD

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Am186/188EM and Am186/188EMLV Microcontrollers

P R E L IMINAR Y

UZI/PIO26

Upper Zero Indicate (output, synchronous)

UZI—This pin lets the designer determine if an access

to the interrupt vector table is in progress by ORing it

with bits 15–10 of the address and data bus (AD15–

AD10 on the 186 and AO15–AO10 on the 188). UZI is

the logical OR of the inverted A19–A16 bits, and it as-

serts in the first period of a bus cycle and is held

throughout the cycle.

This signal should be pulled High or allowed to float at

reset. If this pin is Low at the negation of reset, the

Am186EM and Am188EM microcontrollers will enter a re-

served clock test mode.

VCC

Power Supply (input)

These pins supply power (+5 V) to the microcontroller.

WHB (Am186EM Microcontroller Only)

Write High Byte (output, three-state, synchronous)

This pin and WLB indicate to the system which bytes of

the data bus (upper, lower, or both) participate in a write

cycle. In 80C186 designs, this information is provided by

BHE, AD0, and WR. However, by using WHB and WLB,

the standard system interface logic and external address

latch that were required are eliminated.

WHB is asserted with AD15–AD8. WHB is the logical

OR of BHE and WR. This pin floats during reset.

WLB (Am186EM Microcontroller Only)

WB (Am188EM Microcontroller Only)

Write Low Byte (output, three-state, synchronous)

Write Byte (output, three-state, synchronous)

WLB—This pin and WHB indicate to the system which

bytes of the data bus (upper, lower, or both) participate

in a write cycle. In 80C186 designs, this information is

provided by BHE, AD0, and WR. However, by using

WHB and WLB, the standard system interface logic

and external address latch that were required are elim-

inated.

WLB is asserted with AD7–AD0. WLB is the logical OR

of AD0 and WR. This pin floats during reset.

WB—On the Am188EM microcontroller, this pin indi-

cates a write to the bus. WB uses the same early timing

as the nonmultiplexed address bus. WB is associated

with AD7–AD0. This pin floats during reset.

Write Strobe (output, synchronous)

This pin indicates to the system that the data on the bus

is to be written to a memory or I/O device. WR floats

during a bus hold or reset condition.

Crystal Input (input)

This pin and the X2 pin provide connections for a fun-

damental mode or third-overtone parallel-resonant

crystal used by the internal oscillator circuit. To provide

the microcontroller with an external clock source, con-

nect the source to the X1 pin and leave the X2 pin un-

connected.

Crystal Output (output)

This pin and the X1 pin provide connections for a fun-

damental mode or third-overtone parallel-resonant

crystal used by the internal oscillator circuit. To provide

the microcontroller with an external clock source, leave

the X2 pin unconnected and connect the source to the

X1 pin.

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