STC89LE53RC datasheet(7/165 Pages) STC

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1.4 Pin Descriptions

MNEMONIC

QFP44 PDIP40 PLCC44

DESCRIPTION

P0.0 ~ P0.7

37~30

39~32

43~36 Port0 :Port0 is an 8-bit bi-directional I/O port with pull-up resistance.

Except being as GPIO, Port 0 is also the multiplexed low-order address

and data bus during accesses to external program and data memory.

P1.0 ~ P1.7

40~44

1-8

2~9

Port1 : General-purposed I/O with weak pull-up resistance inside. When

1s are written into Port1, the strong output driving CMOS only turn-on

two period and then the weak pull-up resistance keep the port high.

P1.0 is also used as one of event sources for timer2, or output carrier of

timer 2, alias T2.

P1.1 is also used as one of interrupt-controlling sources for time 2, alias

T2EX.

1~3

P1.0/T2

P1.1/T2EX

P2.0 ~ P2.7

18-25

21-28

24~31 Port2 : Port2 is an 8-bit bi-directional I/O port with pull-up resistance.

Except being as GPIO, Port2 emits the high-order address byte during

accessing to external program and data memory.

P3.0/RxD

Port3 : General-purposed I/O with weak pull-up resistance inside. When

1s are written into Port1, the strong output driving CMOS only turn-on

two period and then the weak pull-up resistance keep the port high. Port3

also serves the functions of various special features.

P3.0 and P3.1 act as receiver and transceiver of the data for UART func-

tion block, Alias RxD and TxD.

P3.2 and P3.3 also act as external interrupt sources, alias /INT0 and

/INT1.

P3.4 and P3.5 also act as event sources for timer0 and timer1 individu-

ally, alias T0 and T1.

P3.6 also acts as write signal while access to external memory,alias /WR.

P3.7 also acts as read signal while access to external memory, alias /RD.

P3.1/TxD

P3.2/INT0

P3.3/INT1

P3.4/T0

P3.5/T1

P3.6/WR

P3.7/RD

P4.0

Port4 : Port4 are extended I/O ports such like Port1. It can be available

only on LQFP-44, PLCC-44.

P4.2 and P4.3 also act as external interrupt sources, alias /INT3 and

/INT2.

P4.1

P4.2/INT3

P4.3/INT2

RST

RESET : A high on this pin for at least two machine cycles will reset the

device.

/EA

EA must be kept at low to enable the device to fetch program code from

external flash memory.

An internal pull-up resistance has been embedded in this pin.

/ALE

Output pulse for latching the low byte of address during accesses to

external memory.

/PSEN

The read strobe to external program memory, low active.

XTAL1

Crystal 1: Input to the inverting oscillator amplifier.Receives the external

oscillator signal when an external oscillator is used.

XTAL2

Crystal 2: Output from the inverting amplifier. This pin should be floated

when an external oscillator is used.

VCC

Power

Gnd

Ground

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