Philips Semiconductors
Product data
P87C51RA2/RB2/RC2/RD2
80C51 8-bit microcontroller family 8KB/16KB/32KB/64KB OTP
with 512B/1KB RAM, low voltage (2.7 to 5.5 V), low power, high
speed (30/33 MHz)
2003 Jan 24
8
MNEMONIC
NAME AND FUNCTION
TYPE
PIN NUMBER
MNEMONIC
NAME AND FUNCTION
TYPE
LQFP
PLCC
PDIP
PSEN
29
32
26
O
Program Store Enable: The read strobe to external program memory. When
executing code from the external program memory, PSEN is activated twice each
machine cycle, except that two PSEN activations are skipped during each access
to external data memory. PSEN is not activated during fetches from internal
program memory.
EA/VPP
31
35
29
I
External Access Enable/Programming Supply Voltage: EA must be externally
held low to enable the device to fetch code from external program memory
locations. If EA is held high, the device executes from internal program memory.
The value on the EA pin is latched when RST is released and any subsequent
changes have no effect. This pin also receives the programming supply voltage
(VPP) during programming.
XTAL1
19
21
15
I
Crystal 1: Input to the inverting oscillator amplifier and input to the internal clock
generator circuits.
XTAL2
18
20
14
O
Crystal 2: Output from the inverting oscillator amplifier.
NOTE:
To avoid “l(fā)atch-up” effect at power-on, the voltage on any pin (other than VPP) must not be higher than VCC + 0.5 V or less than VSS – 0.5 V.