80CL31 Datasheet, PDF (9/40 Pages) NXP Semiconductors – Low-voltage single-chip 8-bit microcontrollers

Philips Semiconductors
Low-voltage single-chip 8-bit microcontrollers
Product specification
80CL31/80CL51
STRONG PULL UP
2 OSCILLATOR PERIODS
+5V
P2
FROM
PORT
LATCH
Q
(a)
P1
P3
I/O PIN
n
INPUT DATA
READ PORT PIN
INPUT BUFFER
(b)
FROM
PORT
LATCH
Q
FROM
PORT
LATCH
Q
INPUT DATA
(c)
READ PORT PIN
STRONG PULL UP
+5V
P1
n
n
I/O PIN
+5V
I/O PIN
EXT.
PULL UP
INPUT BUFFER
Figure 3. Ports
The definition of port options for port 0 is slightly different. Two
cases have to be examined. First, accesses to external memory
(EA=0 or access above the built -in memory boundary), second, I/O
accesses.
External Memory Accesses
Option 1: True 0 and 1 are written as address to the external
memory (strong pull up is used).
Option 2: An external pull up resistor is needed for external
accesses.
Option 3: Not allowed for external memory access as the port can
only be used as output.
I/O Accesses
Option 1: When writing a 1 to the port-latch, the strong pull up p1
will be on for 2 oscillator periods. No weak pull up exists.
Without an external pull up, this option can be used as a
high-impedance input.
Option 2: Open drain; quasi-bidirectional I/O with n-channel open
drain output. Use as an output requires the connection of
an external pull up resistor (see Figure 3(c)).
Option 3: Push-Pull; output with drive capability in both polarities.
Under this option, pins can only be used as outputs.
Individual mask selection of the post-reset state is available on any
of the above pins. Make your selection by appending “S” or “R” to
option 1, 2, or 3 above (e.g. 1 S for a standard I/O to be set after
RESET or 2R for an open-drain I/O to be reset after RESET).
1.3 Timer/event counter
The 80CL51 contains two 16-bit Timer/Counter registers, Timer 0
and Timer 1, which can perform the following functions:
– Measure time intervals and pulse durations
– Count events
– Generate interrupts requests
January 1995
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