P87CL881H 查看數據表（PDF） - Philips Electronics

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P87CL881H

Low-voltage microcontroller with 63-kbyte OTP program memory and 2-kbyte RAM / LQFP44 Package

Philips Electronics 

Philips Semiconductors

Low-voltage microcontroller with 63-kbyte

OTP program memory and 2-kbyte RAM

Product specification

P87CL881H

5.2 Pin description

Table 1 LQFP package

SYMBOL

VDD

VDDP

VSS

VSSP

RST

PORENABLE/VPP

EW

XTAL2

XTAL1

PSEN

ALE

EA

PIN

DESCRIPTION

39 Power supply for core.

38 Power supply for I/O ring.

17 Ground for core.

16 Ground for I/O ring.

4 RESET. A LOW level on this pin for two machine cycles while the oscillator is running,

resets the device. The RST pin is also an output which can be used to reset other ICs.

6 PORENABLE. If set to a logic 1, the internal Power-on reset circuit is enabled. If external

reset circuitry is used, it is recommended to keep PORENABLE LOW in order to achieve

the lowest power consumption. This pin is also used for the OTP programming voltage

VPP.

28 Enable Watchdog Timer.

14 Crystal output. Output of the amplitude controlled oscillator. If an external oscillator

clock is used this pin not used.

15 Crystal input. Input to the amplitude controlled oscillator. Also the input for an externally

generated clock source.

26 Program Store Enable. Read strobe to external program memory. When executing

code out of external program memory, PSEN is activated twice each machine cycle.

However, during each access to external data memory two PSEN activations are

skipped. During Power-down mode the PSEN pin stays HIGH.

27 Address Latch Enable. Latches the low byte of the address during accesses to external

memory. It is activated every six oscillator periods and may be used for external timing or

clocking purposes. For improved EMC behaviour, the toggle of the ALE pin can be

disabled by setting the RFI bit in the PCON register by software. This bit is cleared on

reset and can be set and cleared by software. When set, the ALE pin will be pulled-down

internally, switching an external address latch to a quiet state. The MOVX instruction will

still toggle ALE if external memory is accessed. ALE will retain its normal HIGH state

during Idle mode and a LOW state during the Power-down mode while in the EMC mode.

Additionally, during internal access (EA = 1) ALE will toggle normally when the address

exceeds the internal program memory size. During external access (EA = 0) ALE will

always toggle normally, whether the RFI bit is set or not.

29 External Access. When EA is held HIGH, the CPU executes out of the internal program

memory (unless the program counter exceeds the highest address for internal program

memory). When EA is held LOW, the CPU executes out of external program memory

regardless of the value of the program counter. The state of the EA pin is internally

latched at reset.

1999 Apr 16

6

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