P89V51RB2BA データシートの表示（PDF） - Philips Electronics

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P89V51RB2BA

8-bit 80C51 5 V low power 16/32/64 kB Flash microcontroller with 1 kB RAM

Philips Electronics 

Philips Semiconductors

P89V51RB2/RC2/RD2

8-bit microcontrollers with 80C51 core

Table 3:

Symbol

EA

P89V51RB2/RC2/RD2 pin description…continued

Pin

Type

DIP40

TQFP44 PLCC44

31

29

35

I

ALE/

30

27

33

I/O

PROG

NC

-

XTAL1 19

XTAL2 18

VDD

40

VSS

20

6, 17, 28, 1, 12, 23, I/O

39

34

15

21

I

14

20

O

38

44

I

16

22

I

Description

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. However, Security lock

level 4 will disable EA, and program execution is only

possible from internal program memory. The EA pin can

tolerate a high voltage of 12 V.

Address Latch Enable: ALE is the output signal for

latching the low byte of the address during an access to

external memory. This pin is also the programming

pulse input (PROG) for flash programming. 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.

No Connect

Crystal 1: Input to the inverting oscillator amplifier and

input to the internal clock generator circuits.

Crystal 2: Output from the inverting oscillator amplifier.

Power supply

Ground

[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 kΩ to 50 kΩ to VDD, e.g., for ALE pin.

[2] For 6-clock mode, ALE is emitted at 1⁄3 of crystal frequency.

9397 750 14341

Product data

Rev. 03 — 02 December 2004

© Koninklijke Philips Electronics N.V. 2004. All rights reserved.

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