P R E L I M I N A R Y
dress latch enable (ALE) signal is no longer needed.
KEY FEATURES AND BENEFITS
Individual byte-write-enable signals are provided to
eliminate the need for external high/low byte-write-en-
able circuitry. The maximum bank size that is program-
mable for the memory chip-select signals has been
increased to facilitate the use of high-density memory
devices.
The Am186EM and Am188EM microcontrollers extend
the AMD family of microcontrollers based on the indus-
try-standard x86 architecture. The Am186EM and
Am188EM microcontrollers are higher-performance,
more integrated versions of the 80C186/188 micropro-
cessors, offering a migration path that was previously
unavailable. Upgrading to the Am186EM and
Am188EM microcontrollers is an attractive solution for
several reasons:
The improved memory timing specifications for the
Am186EM and Am188EM microcontrollers allow no
wait-state operation with 70-ns memory access times
at a 40-MHz CPU clock speed. This reduces overall
system cost significantly by allowing the use of a more
commonly available memory speed and technology.
n Minimized total system cost—New peripherals and
on-chip system interface logic on the Am186EM and
Am188EM microcontrollers reduce the cost of existing
80C186/188 designs.
Direct Memory Interface Example
n X86 software compatibility—80C186/188-com-
patible and upward-compatible with the other mem-
bers of the AMD E86 family.
Figure 1 illustrates the Am186EM microcontroller direct
memory interface. The processor A19–A0 bus con-
nects to the memory address inputs, the AD bus con-
nects to the data inputs and outputs, and the chip
selects connect to the memory chip-select inputs.
n Enhanced performance—The Am186EM and
Am188EM microcontrollers increase the perfor-
mance of 80C186/188 systems, and the demulti-
plexed address bus offers faster, unbuffered access
to memory.
The RD output connects to the SRAM Output Enable
(OE) pin for read operations. Write operations use the byte
write enables connected to the SRAM Write Enable (WE)
pins.
n Enhanced functionality—The new and enhanced
on-chip peripherals of the Am186EM and Am188EM
microcontrollers include an asynchronous serial
port, 32 PIOs, a watchdog timer, an additional inter-
rupt pin, a synchronous serial interface, a PSRAM
controller, a 16-bit reset configuration register, and
enhanced chip-select functionality.
The example design uses 2-Mbit memory technology
(256 Kbytes) to fully populate the available address
space. Two flash PROM devices provide 512 Kbytes of
nonvolatile program storage and two static RAM de-
vices provide 512 Kbytes of data storage area.
Figure 1 also shows an implementation of an RS-232
console or modem communications port. The RS-232-
to-CMOS voltage-level converter is required for the
electrical interface with the external device.
Application Considerations
The integration enhancements of the Am186EM and
Am188EM microcontrollers provide a high-perfor-
mance, low-system-cost solution for 16-bit embedded
microcontroller designs. The nonmultiplexed address
bus eliminates the need for system-support logic to in-
terface memory devices, while the multiplexed ad-
dress/data bus maintains the value of previously
engineered, customer-specific peripherals and circuits
within the upgraded design.
Am186EM
Microcontroller
Flash PROM
X2
WHB
WLB
WE
WE
X1
Address
A19–A0
40-MHz
Crystal
Figure 1 illustrates an example system design that
uses the integrated peripheral set to achieve high per-
formance with reduced system cost.
Data
OE
AD15–AD0
RD
CS
UCS
Clock Generation
The integrated clock generation circuitry of the
Am186EM and Am188EM microcontrollers allows the
use of a times-one crystal frequency. The design in
Figure 1 achieves 40-MHz CPU operation while using
a 40-MHz crystal.
Static RAM
WE
WE
Serial Port
RS-232
Level
Converter
TXD
RXD
Address
Data
OE
Memory Interface
The integrated memory controller logic of the
Am186EM and Am188EM microcontrollers provides a
direct address bus interface to memory devices. The
use of an external address latch controlled by the ad-
LCS
CS
Figure 1. Example System Design
10
Am186/188EM and Am186/188EMLV Microcontrollers
AMD [ AMD ]
