ST6373 Datasheet, PDF (34/64 Pages) STMicroelectronics – 8-BIT ROM/OTP/EPROM MCUs FOR DIGITALLY CONTROLLED MULTISYNC/MULTISTANDARD MONITORS

ST6373
4.1.3 I/O Port Registers
4.1.3.1 Data Registers
Ports A, B, C Data Register
Address: C0h (PA), C1h (PB), C2h (PC) -
Read/Write
Reset Value: 00h
7
0
PA/PB PA/P B PA/PB PA/PB PA/PB PA/PB PA/PB PA/PB
/PC7 /PC6 /PC5 /PC4 /PC3 /PC2 /PC1 /PC0
PA7-PA0. These are the I/O Port A data bits. Re-
set at power-on.
PB7-PB0. These are the I/O Port B data bits. Re-
set at power-on.
PC7-PC0. These are the I/O Port C data bits. Set
to 04H at power-on. Bit 2 (PC2 pin) is set to one
(open-drain therefore high impedance).
4.1.3.2 Data Direction Registers
Ports A, B, C Data Direction Register
Address: C4h (PA), C5h (PB), C6h (PC) -
Read/Write
Reset Value: 00h
7
0
PA/PB PA/P B PA/PB PA/PB PA/PB PA/PB PA/PB PA/PB
/PC7 /PC6 /PC5 /PC4 /PC3 /PC2 /PC1 /PC0
PA7-PA0. These are the I/O Port A data direction
bits. When a bit is cleared to zero the related I/O
line is in input mode, if bit is set to one the related
I/O line is in output mode. Reset at power-on.
PB7-PB0. These are the I/O Port B data direction
bits. When a bit is cleared to zero the related I/O
line is in input mode, if bit is set to one the related
I/O line is in output mode. Reset at power-on.
PC7-PC0. These are the I/O Port C data direction
bits. When a bit is cleared to zero the related I/O
line is in input mode, if bit is set to one the related
I/O line is in output mode. Set to 04H at power-on.
Bit 2 (PC2 pin) is set to one (output mode select-
ed).
4.1.3.3 Option Registers
Port A, B, C Option Register
Address: CCh (PA), CDh (PB) - Read/Write
Reset value:00h
7
0
PA/PB7 PA/PB6 PA/PB5 PA/P B4PA/PB3 PA/PB2 PA/PB1 PA/P B0
PA7-PA0. These are the I/O Port A option bits.
These are set in conjunction with the correspond-
ing data and data direction bits to set the individual
Port A bit I/O mode.
PB7-PB0. These are the I/O Port B option bits.
These are set in conjunction with the correspond-
ing data and data direction bits to set the individual
Port B bit I/O mode.
Notes: The WAIT instruction allows the MCU to be
used in situations where low power consumption is
required. This can only be achieved, however, if
the I/O pins are programmed as inputs with well
defined logic levels or have no power consuming
resistive loads in output mode.
Single-bit operations on I/O registers are possible
but care is necessary because reading in input
mode is from I/O pins while writing will directly af-
fect the Port data register.
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