P80C557E4 查看數據表（PDF） - Philips Electronics

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P80C557E4

Single-chip 8-bit microcontroller

Philips Electronics 

Philips Semiconductors

Single-chip 8-bit microcontroller

Product specification

P83C557E4/P80C557E4/P89C557E4

PIN DESCRIPTION (Continued)

SYMBOL

P3.0 – P3.7

N.C.

XTAL2

XTAL1

P2.0 – P2.7

PSEN

ALE/WE

EA

P0.7–P0.0

XTAL3

XTAL4

SELXTAL1

PIN

41 – 48

49 – 50

51

52

55 – 62

63

64

65

68 –75

78

79

80

DESCRIPTION

8-bit quasi-bidirectional I/O port

Port pin

Alternative function

P3.0

RXD :

Serial input port

P3.1

TXD :

Serial output port

P3.2

INT0 :

External interrupt

P3.3

INT1 :

External interrupt

P3.4

T0

:

Timer 0 external input

P3.5

T1

:

Timer 1 external input

P3.6

WR

:

External data memory write strobe

P3.7

RD

:

External data memory read strobe

Not connected pins.

Crystal pin 2: output of the inverting amplifier that forms the oscillator. Left open-circuit when an external

oscillator clock is used.

Crystal pin 1: input to the inverting amplifier that forms the oscillator, and input to the internal clock

generator. Receives the external oscillator clock signal when an external oscillator is used. Must be

connected to logic HIGH if the PLL oscillator is selected (SELXTAL1 = LOW).

Port2: 8-bit quasi-bidirectional I/O port with internal pull-ups.During access to external memories

(RAM/ROM) that use 16-bit addresses (MOVX@DPTR) Port 2 emits the high order address byte. The

alternative function of P2.7 for the P89C557E4 is the output enable signal for verify/read modes (active low).

Port 2 can sink/source one TTL (=4 LSTTL) input. It can drive CMOS inputs without external pull-ups.

Program Store Enable output: read strobe to the external program memory via Port 0 and 2. Is activated

twice each machine cycle during fetches from external program memory. When executing out of external

program memory two activations of PSEN are skipped during each access to external data memory. PSEN

is not activated (remains HIGH) during no fetches from external program memory. PSEN can sink/source 8

LSTTL inputs. It can drive CMOS inputs without external pull-ups.

Address Latch Enable output: latches the low byte of the address during access of external memory in

normal operation. It is activated every six oscillator periods except during an external data memory access.

ALE/WE can sink/-source 8 LSTTL inputs. It can drive CMOS inputs without an external pull-up. The

alternative function for the P89C557E4 is the programming pulse input WE.

To prohibit the toggling of ALE pin (RFI noise reduction) the bit RFI in the PCON Register (PCON.5) must be

set by software. This bit is cleared on RESET and can be set and cleared by software. When set, 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 value during Idle Mode and a low value during Power-down Mode while in the

“RFI” 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 flag “RFI” is set or not.

External Access Input: If, during RESET, EA is held at a TTL level HIGH the CPU executes out of the

internal program memory, provided the program counter is less than 32768. If, during RESET, EA is held at a

TTL level LOW the CPU executes out of external program memory via Port 0 and Port 2. EA is not allowed

to float. EA is latched during RESET and don’t care after RESET.

Port 0: 8-bit open drain bidirectional I/O port. It is also the multiplexed low-order address and data bus during

accesses to external memory (during theses accesses internal pull-ups are activated). Port 0 can sink/source

8 LSTTL inputs.

Crystal pin, output of the inverting amplifier that forms the 32 kHz oscillator

Crystal pin, input to the inverting amplifier that forms the 32 kHz oscillator. XTAL3 and XTAL4 are pulled

LOW if the PLL oscillator is not selected (SELXTAL1 = HIGH) or if Reset is active.

Must be connected to logic HIGH level to select the HF oscillator, using the XTAL1/XTAL2 crystal. If pulled low

the PLL is selected for clocking of the controller, using the XTAL3/ XTAL4 crystal.

NOTE:

1. To avoid a ‘latch-up’ effect at Power-on, the voltage at any pin at any time must not be higher or lower than VDD+ 0.5 V or VSS– 0.5 V

respectively.

1999 Mar 02

7

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