AM186ES Advanced Micro Devices, AM186ES Datasheet - Page 51

• Manufacturer Part Number: AM186ES
• Description: microcontrollers provide a low-cost/ high-performance solution for embedded system designers who wish to use the x86 architecture.
• Manufacturer: Advanced Micro Devices

3.1.1
WR
X1
X2
Pins That Are Used by Emulators
The following pins are used by emulators: A19–A0, AO15–AO8, AD7–AD0, ALE, BHE/
ADEN (on the 186), CLKOUTA, RFSH2/ADEN (on the 188), RD, S2–S0, S6/LOCK/
CLKDIV2, and UZI.
Emulators require S6/LOCK/CLKDIV2 and UZI be configured in their normal functionality,
that is as S6 and UZI.
If BHE/ADEN (on the 186) or RFSH2/ADEN (on the 188) is held Low during the rising edge
of RES, S6 and UZI are configured in their normal functionality, instead of as PIOs, at reset.
WB—On the Am188ES microcontroller, this pin indicates 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)
WR—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 fundamental mode or
third-overtone, parallel-resonant crystal used by the internal oscillator
circuit. To provide the microcontroller with an external clock source,
connect the source to the X1 pin and leave the X2 pin unconnected.
Crystal Output (output)
This pin and the X1 pin provide connections for a fundamental 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.
System Overview
3-19