AM186ES-40VCW datasheet(51/102 Pages) AMD

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Am186/188ES and Am186/188ESLV Microcontrollers

P R E L IMINA R Y

PULSE WIDTH DEMODULATION

For many applications, such as bar-code reading, it is

necessary to measure the width of a signal in both its

High and Low phases. The Am186ES and Am188ES

microcontrollers provide a pulse-width demodulation

(PWD) option to fulfill this need. The PWD bit in the

system configuration register (SYSCON) enables the

PWD option. Please note that the Am186ES and

Am188ES microcontrollers do not support analog-to-

digital conversion.

In PWD mode, TMRIN0, TMRIN1, INT2, and INT4 are

configured internal to the microcontroller to support the

detection of rising and falling edges on the PWD input

pin (INT2/INTA0/PWD) and to enable either timer 0

when the signal is High or timer 1 when the signal is

Low. The INT4, TMRIN0, and TMRIN1 pins are not

used in PWD mode and so are available for use as

PIOs.

The following diagram shows the behavior of a system

for a typical waveform.

The interrupt service routine (ISR) for the INT2 and

INT4 interrupts should examine the current count of the

associated timer, timer 1 for INT2 and timer 0 for INT4,

in order to determine the pulse width. The ISR should

then reset the timer count register in preparation for the

next pulse.

Since the timers count at one quarter of the processor

clock rate, this determines the maximum resolution that

can be obtained. Further, in applications where the

pulse width may be short, it may be necessary to poll

the INT2 and INT4 request bits in the interrupt request

ing and returning from an interrupt. Overflow condi-

tions, where the pulse width is greater than the

maximum count of the timer, can be detected by mon-

itoring the Maximum Count (MC) bit in the associated

timer or by setting the INT bit to enable timer interrupt

requests.

ASYNCHRONOUS SERIAL PORTS

The Am186ES and Am188ES microcontrollers provide

two independent asynchronous serial ports. These

ports provide full-duplex, bidirectional data transfer

using several industry-standard communications pro-

tocols. The serial ports can be used as sources or des-

tinations of DMA transfers.

The asynchronous serial ports support the following

features:

n Full-duplex operation

n 7-bit, 8-bit, or 9-bit data transfers

n Odd, even, or no parity

n One stop bit

n Two lengths of break characters

n Error detection

— Parity errors

— Framing errors

— Overrun errors

n Hardware handshaking with the following select-

able control signals:

— Clear-to-send (CTS)

— Enable-receiver-request (ENRX)

— Ready-to-send (RTS)

— Ready-to-receive (RTR)

n DMA to and from the serial ports

n Separate maskable interrupts for each port

n Multidrop protocol (9-bit) support

n Independent baud rate generators

n Maximum baud rate of 1/16th of the CPU clock

n Double-buffered transmit and receive

DMA Transfers through the Serial Port

The Am186ES and Am188ES microcontrollers support

DMA transfers both to and from the serial port. Either

or both DMA channels and either or both serial ports

can be used for DMA transmits or receives. See the

DMA Control register descriptions in the

Am186ES and

Am188ES Microcontrollers User’s Manual for more in-

formation.

INT2

INT4

INT2

Ints generated

TMR1 enabled

TMR0 enabled

AM186ES-40VCW 数据表(PDF) 51 Page - Advanced Micro Devices

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