System Overview
3-1
CHAPTER
3
SYSTEM OVERVIEW
This chapter contains descriptions of the Am186EM and Am188EM microcontroller pins,
the bus interface unit, the clock and power management unit, and power-save operation.
3.1
PIN DESCRIPTIONS
Pin Terminology
The following terms are used to describe the pins:
Input—An input-only pin.
Output—An output-only pin.
Input/Output—A pin that can be either input or output.
Synchronous—Synchronous inputs must meet setup and hold times in relation to
CLKOUTA. Synchronous outputs are synchronous to CLKOUTA.
Asynchronous—Inputs or outputs that are asynchronous to CLKOUTA.
A19–A0
Address Bus (output, three-state, synchronous)
The A19–A0 pins supply nonmultiplexed memory or I/O addresses to
the system one-half of a CLKOUTA period earlier than the multiplexed
address and data bus (AD15–AD0 on the Am186EM or AO15–AO8 and
AD7–AD0 on the Am188EM). During a bus hold or reset condition, the
address bus is in a high-impedance state.
AD7–AD0
Address and Data Bus
(input/output, three-state, synchronous, level-sensitive)
These time-multiplexed pins supply partial memory or I/O addresses,
as well as data, to the system. This bus supplies the low-order 8 bits of
an address to the system during the first period of a bus cycle (t
1
), and
it supplies data to the system during the remaining periods of that cycle
(t
2
, t
3
, and t
4
).
The address phase of these pins can be disabled. See the ADEN
description with the BHE/ADEN pin. When WLB is not asserted, these
pins are three-stated during t
2
, t
3
, and t
4
.
During a bus hold or reset condition, the address and data bus is in a
high-impedance state.
During a power-on reset, the address and data bus pins (AD15–AD0
for the Am186EM, AO15–AO8 and AD7–AD0 for the Am188EM) can
also be used to load system configuration information into the internal
Reset Configuration register.
Содержание AM186EM
Страница 1: ...Am186 EM and Am188 EM Microcontrollers User s Manual...
Страница 4: ...iv...
Страница 12: ...Table of Contents xii...
Страница 62: ...Peripheral Control Block 4 10...
Страница 76: ...Chip Select Unit 5 14...
Страница 122: ...Timer Control Unit 8 8...
Страница 136: ...DMA Controller 9 14...
Страница 144: ...Asynchronous Serial Port 10 8...
Страница 158: ...Programmable I O Pins 12 6...
Страница 186: ...Index I 12...