P89V52X2FN datasheet(7/56 Pages) PHILIPS

7 / 56 page

P89V52X2_1

Preliminary data sheet

Rev. 01 — 7 June 2007

7 of 56

NXP Semiconductors

P89V52X2

80C51 with 256 B RAM, 192 B data EEPROM

[1]

ALE loading issue: When ALE pin experiences higher loading (>30 pF) during the reset, the microcontroller may accidentally enter into

modes other than normal working mode. The solution is to add a pull-up resistor of 3 k

Ω to 50 kΩ to V

DD, e.g., for ALE pin.

[2]

For 6-clock mode, ALE is emitted at 1

⁄

3 of crystal frequency.

P3.5/T1/CEX4 15

I/O

P3.5 — Port 3 bit 5.

T1 — External count input to Timer/Counter 1

P3.6/WR

P3.6 — Port 3 bit 6.

WR — External data memory write strobe

P3.7/RD

P3.7 — Port 3 bit 7.

RD — External data memory read strobe.

PSEN

I/O

Program Store Enable: PSEN is the read strobe for

external program memory. When the device is executing

from internal program memory, PSEN is inactive (HIGH).

When the device is executing code from external program

memory, PSEN is activated twice each machine cycle,

except that two PSEN activations are skipped during each

access to external data memory.

RST

9410

Reset: While the oscillator is running, a HIGH logic state

on this pin for two machine cycles will reset the device.

External Access Enable: EA must be connected to VSS in

order to enable the device to fetch code from the external

program memory. EA must be strapped to VDD for internal

program execution.

ALE

2733I/O

Address Latch Enable: ALE is the output signal for

latching the low byte of the address during an access to

external memory. Normally the ALE[1] is emitted at a

constant rate of 1

⁄

6 the crystal frequency

[2] and can be

used for external timing and clocking. One ALE pulse is

skipped during each access to external data memory.

However, if AO is set to ‘1’, ALE is disabled.

XTAL1

Crystal 1: Input to the inverting oscillator amplifier and

input to the internal clock generator circuits.

XTAL2

Crystal 2: Output from the inverting oscillator amplifier.

VDD

Power supply

VSS

Ground

Table 2.

Pin description …continued

Symbol

Type

Description

DIP40

LQFP44

PLCC44

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