8XC151SASB HIGH-PERFORMANCE CHMOS MICROCONTROLLER

Table 7 Signal Descriptions

(Continued)

Signal

Type

Description

Multiplexed

Name

With

P30

IO

Port 3

This is an 8-bit bidirectional IO port with internal pullups

RXD

P31

TXD

P332

INT10

P354

T10

P36

WR

P37

RD

PSEN

O

Program Store Enable

Read signal output This output is asserted

for a memory address range that depends on bits RD0 and RD1 in

configuration byte UCONFIG0

RD

O

Read

Read signal output to external data memory

P37

RST

I

Reset

Reset input to the chip Holding this pin high for 64 oscillator

periods while the oscillator is running resets the device The port pins

applied whether or not the oscillator is running This pin has an

internal pulldown resistor which allows the device to be reset by

Asserting RST when the chip is in idle mode or powerdown mode

returns the chip to normal operation

RXD

IO

Receive Serial Data

RXD sends and receives data in serial IO

P30

mode 0 and receives data in serial IO modes 1 2 and 3

T10

I

Timer 10 External Clock Inputs

When timer 10 operates as a

P354

counter a falling edge on the T10 pin increments the count

T2

IO

Timer 2 Clock InputOutput

For the timer 2 capture mode this

P10

signal is the external clock input For the clock-out mode it is the

timer 2 clock output

T2EX

I

Timer 2 External Input

In timer 2 capture mode a falling edge

P11

initiates a capture of the timer 2 registers In auto-reload mode a

falling edge causes the timer 2 registers to be reloaded In the up-

down counter mode this signal determines the count direction

1 e up 0 e down

TXD

O

Transmit Serial Data

TXD outputs the shift clock in serial IO mode

P31

0 and transmits serial data in serial IO modes 1 2 and 3

PWR

Supply Voltage

Connect this pin to the a5V supply voltage

PWR

Secondary Supply Voltage 2

This supply voltage connection is

provided to reduce power supply noise Connection of this pin to the

a

5V supply voltage is recommended However when using the

can be unconnected without loss of compatibility (Not available on

DIP)

I

Programming Supply Voltage

The programming supply voltage is

EA

applied to this pin for programming the on-chip OTPROM

The descriptions of A158P270 and AD70P070 are for the nonpage-mode chip configuration (compatible with

44-lead PLCC and 40-pin DIP MCS 51 microcontrollers) If the chip is configured for page-mode operation port 0 carries

the lower address bits (A70) and port 2 carries the upper address bits (A158) and the data (D70)

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