Direct Memory Interface Example
Figure 1 illustrates the direct interface to memory of the
Am186ER microcontroller. The A19–A0 bus connects
to the memory address inputs, the AD bus connects to
the data inputs and outputs, and the chip selects con-
nect to the memory chip-select inputs.
Am29F400
Flash
Am186ER
Microcontroller
WR
WE
X2
12.5-MHz
Crystal
A19–A0
Address
X1
Data
AD15–AD0
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.
OE
RD
CS
UCS
32 Kbyte
SRAM
COMPARISON OF THE Am186™ER AND
Timer 0–2
80C186 MICROCONTROLLERS
INT4–INT0
DMA 0–1
Serial Port
Figure 1 shows an example system using a 50-MHz
Am186ER microcontroller. Figure 2 shows a compara-
ble system implementation with an 80C186 microcon-
troller. Because of its superior integration, the
Am186ER system does not require the support devices
required on the 80C186 example system. In addition,
the Am186ER microcontroller provides significantly
better performance with its 50-MHz clock rate.
RS-232
Level
Converter
TXD
RXD
50 MHz
CLKOUTA
Figure 1. Am186™ER 50-MHz Example
System Design
X2
X1
BHE
A0
40-MHz
Crystal
SRAM
Am29F400
Flash
WE
WE
WR
ALE
WE
Address
Data
Address
AD15–AD0
Data
OE
OE
RD
UCS
LCS
CS
CS
LATCH
PIOs
RS-232
Level
Converter
Serial
Port
PCS0
Timer 0–2
INT3
INT2–INT0
DMA 0–1
20 MHz
CLKOUT
Figure 2. Typical 80C186 System Design
Am186TMER and Am188TMER Microcontrollers Data Sheet
15
AMD [ AMD ]
