system form factor, decreased system power, stable
RAM supply, and lower system cost compared with
buying external SRAM. The integrated RAM also en-
sures that an entire embedded system will not require
requalification based on the short life cycles of external
SRAM. Additionally, for those systems using more
RAM than required because of the granularity of exter-
nal RAM, the Am186ER microcontroller provides a
closer system match.
KEY FEATURES AND BENEFITS
The Am186ER and Am188ER microcontrollers are
higher-performance, highly integrated versions of the
80C186/80C188 microprocessors, offering a migration
path that was previously unavailable. New peripherals,
on-chip system interface logic, and 32 Kbyte of internal
memory on the Am186ER microcontroller reduce the
cost of existing 80C186/80C188 designs. Upgrading to
the Am186ER microcontroller is an attractive solution
for several reasons:
Clock Generation
The integrated clock generation circuitry of the
Am186ER and Am188ER microcontrollers enables the
processors to operate at up to four times the crystal fre-
quency. The design in Figure 1 achieves 50-MHz CPU
operation while using a 12.5-MHz crystal. The clocking
frequency function is controlled by an internal PLL. The
following modes are available (see Figure 10 on page
48):
n Integrated SRAM—32 Kbyte of internal SRAM en-
sures a low-cost supply of memory and a smaller
form factor for system designs. The internal mem-
ory provides the same performance as external
zero-wait-state SRAM devices.
n 3.3-V operation with 5-V-tolerant I/O—3.3-V oper-
ation provides much lower power consumption
when compared to existing 5-V designs. Plus, the
Am186ER and Am188ER controllers accommodate
current 5-V designs with 5-V-tolerant I/O drivers.
n Divide by Two—The frequency of the fundamental
clock is half the frequency of the crystal with the PLL
disabled.
n x86 software compatibility—80C186/80C188-
compatible and upward-compatible with the other
members of the AMD E86 family.
n Times One—The frequency of the fundamental
clock will be the same as the external crystal with
the PLL enabled.
n Enhanced performance—The Am186ER and
Am188ER microcontrollers increase the perfor-
mance of 80C186/80C188 systems, and the non-
multiplexed address bus offers faster, unbuffered
access to commodity-speed, external memory.
n Times Four—The frequency of the fundamental
clock is four times the frequency of the crystal with
the PLL enabled.
The default mode is Times Four.
n Enhanced
functionality—Enhanced
on-chip
Memory Interface
peripherals include an asynchronous serial port, up
to 32 PIOs, a hardware watchdog timer, an
additional interrupt pin, a synchronous serial
interface, a PSRAM controller, a 16-bit reset
configuration register, and enhanced chip-select
functionality.
The integrated memory controller logic of the
Am186ER and Am188ER microcontrollers provides a
direct address bus to memory devices. Using an exter-
nal address latch controlled by the address latch en-
able (ALE) signal is no longer necessary. Individual
byte-write-enable signals on the Am186ER and
Am188ER microcontrollers eliminate the need for ex-
ternal high/low byte-write-enable circuitry. The maxi-
mum bank size programmable for the memory chip-
select signals is increased to facilitate the use of high-
density memory devices.
Application Considerations
The integration enhancements of the Am186ER micro-
controller provide a high-performance, low-system-
cost solution for 16-bit embedded microcontroller de-
signs. Both multiplexed and nonmultiplexed address
buses are available on the Am186ER and Am188ER
microcontrollers. The nonmultiplexed address bus
eliminates system-support logic ordinarily needed to
interface with external memory devices, while the mul-
tiplexed address/data bus maintains the value of previ-
ously engineered, customer-specific peripherals and
circuits within the upgraded design. Figure 1 on page
15 illustrates an example system design that uses the
integrated peripheral set to achieve high performance
with reduced system cost.
The improved memory timing specifications for the
Am186ER and Am188ER microcontrollers facilitate the
use of external memory devices with 55-ns access
times at 50-MHz CPU operation. As a result, overall
system cost is significantly reduced as system design-
ers are able to use commonly available memory tech-
nology.
Internal Memory
The 32-Kbyte internal RAM fulfills the memory require-
ments for many embedded systems. These systems
can take advantage of the increased reliability, smaller
14
Am186TMER and Am188TMER Microcontrollers Data Sheet
AMD [ AMD ]
