P8XC557E4 NXP Semiconductors, P8XC557E4 Datasheet - Page 7

• Manufacturer Part Number: P8XC557E4
• Description: The P80C557E4/P83C557E4/P89C557E4 (hereafter generically referred to as P8xC557E4) single-chip 8-bit microcontroller is manufactured in an advanced CMOS process and is a derivative of the 80C51 microcontroller family
• Manufacturer: NXP Semiconductors

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 V
Philips Semiconductors
PIN DESCRIPTION (Continued)
NOTE:
1999 Mar 02
SYMBOL
P3.0 – P3.7
N.C.
XTAL2
XTAL1
P2.0 – P2.7
PSEN
ALE/WE
EA
P0.7–P0.0
XTAL3
XTAL4
SELXTAL1
Single-chip 8-bit microcontroller
respectively.
PIN
49 – 50
41 – 48
51
52
55 – 62
63
64
65
68 –75
78
79
80
DESCRIPTION
8-bit quasi-bidirectional I/O port
Port pin
P3.0
P3.1
P3.2
P3.3
P3.4
P3.5
P3.6
P3.7
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.
Alternative function
RXD
TXD
INT0
INT1
T0
T1
WR
RD
:
:
:
:
:
:
:
:
7
Serial input port
Serial output port
External interrupt
External interrupt
Timer 0 external input
Timer 1 external input
External data memory write strobe
External data memory read strobe
P83C557E4/P80C557E4/P89C557E4
DD
+ 0.5 V or V
Product specification
SS
– 0.5 V