PIC16C558T-04/SO View Datasheet(PDF) - Microchip Technology
Part Name
Description
Manufacturer
PIC16C558T-04/SO Datasheet PDF : 108 Pages
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5.0 I/O PORTS
The PIC16C554 and PIC16C558 have two ports,
PORTA and PORTB. The PIC16C557 has three ports,
PORTA, PORTB and PORTC.
5.1 PORTA and TRISA Registers
PORTA is a 5-bit wide latch. RA4 is a Schmitt Trigger
input and an open-drain output. Port RA4 is multiplexed
with the T0CKI clock input. All other RA port pins have
Schmitt Trigger input levels and full CMOS output driv-
ers. All pins have data direction bits (TRIS registers)
which can configure these pins as input or output.
A '1' in the TRISA register puts the corresponding out-
put driver in a Hi-impedance mode. A '0' in the TRISA
register puts the contents of the output latch on the
selected pin(s).
Reading the PORTA register reads the status of the
pins, whereas writing to it will write to the port latch. All
write operations are read-modify-write operations. So a
write to a port implies that the port pins are first read,
then this value is modified and written to the port data
latch.
Note 1: On RESET, the TRISA register is set to all
inputs.
FIGURE 5-1:
BLOCK DIAGRAM OF
PORT PINS RA<3:0>
Data
Bus
WR
PORTA
WR
TRISA
D
Q
CK
Q
Data Latch
D
Q
CK
Q
TRIS Latch
RD TRISA
VDD
P
VDD
N
I/O pin
VSS
VSS
Schmitt
Trigger
input
buffer
Q
D
EN
RD PORTA
PIC16C55X
FIGURE 5-2:
BLOCK DIAGRAM OF RA4
PIN
Data
bus
WR
PORTA
DQ
CK Q
WR
TRISA
Data Latch
DQ
CK Q
TRISA Latch
N
I/O pin(1)
VSS
VSS
Schmitt
Trigger
input
buffer
RD TRISA
Q
D
EENN
RD PORTA
TMR0 clock input
2002 Microchip Technology Inc.
Preliminary
DS40143D-page 23
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