80C575 Datasheet, PDF (6/40 Pages) NXP Semiconductors – 80C51 8-bit microcontroller family 8K/256 OTP/ROM/ROMless, 4 comparator, failure detect circuitry, watchdog timer

Philips Semiconductors
80C51 8-bit microcontroller family
8K/256 OTP/ROM/ROMless, 4 comparator, failure detect circuitry, watchdog timer
Product specification
80C575/83C575/
87C575
PIN DESCRIPTIONS (Continued)
PIN NUMBER
MNEMONIC DIP LCC QFP TYPE NAME AND FUNCTION
Port 3: (continued)
10
11
5
I P3.0 RxD Serial receive port
11
13
7
O P3.1 TxD
Serial transmit port enabled only when transmitting serial data
12
14
8
I P3.2 INT0 External interrupt 0
13
15
9
I P3.3 INT1 External interrupt 1
14
16
10
I P3.4 T0
Timer/counter 0 input
CMPR- Common - reference to comparators 1, 2, 3
15
17
11
I P3.5 T1
Timer/counter 1 input
CMP1+ Comparator 1 positive input
16
18
12
O P3.6 WR
External data memory write strobe
CMP2+ Comparator 2 positive input
17
19
13
O P3.7 RD
External data memory read strobe
CMP3+ Comparator 3 positive input
RST
9
10
4
I Reset: A low on this pin asynchronously resets all port pins to a low state except P3.1. The
pin must be held low with the oscillator running for 24 oscillator cycles to initialize the
internal registers. An internal diffused resistor to V_CC permits a power on reset using only
an external capacitor to V_SS. RST has a Schmitt trigger input stage to provide additional
noise immunity with a slow rising input voltage.
ALE/PROG 30
33
27
I/O Address Latch Enable/Program Pulse: Output pulse for latching the low byte of the
address during an access to external memory. In normal operation, ALE is emitted at a
constant rate of 1/6 the oscillator frequency, and can be used for external timing or clocking.
Note that one ALE pulse is skipped during each access to external data memory. ALE is
switched off if the bit 0 in the AUXR register (8EH) is set. This pin is also the program pulse
input (PROG) during EPROM programming.
PSEN
29
32
26
O Program Store Enable: The read strobe to external program memory. When the device is
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/V_PP
XTAL1
31
35
29
19
21
15
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 0000H to
1FFFH. If EA is held high, the device executes from internal program memory unless the
program counter contains an address greater than 1FFFH. This pin also receives the
12.75V programming supply voltage (V_PP) during EPROM programming.
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.
1998 May 01
6