ST52T400/T440/E440/T441
6 I/O PORTS
6.1 Introduction
ST52x400/440/441 devices offer flexible individu-
ally programmable multi-functional input/output
lines. Refer to Chapter 1 for specific pin alloca-
tions.
21 I/O lines, grouped in 3 different ports, are avail-
able for ST52x400G/440G/441G devices:
PORT A = 8-bit ports (PA0 - PA7 pins)
PORT B = 8-bit ports (PB0 - PB7 pins)
PORT C = 5-bit port (PC0 - PC4 pins)
13 I/O lines, grouped in 2 different ports are avail-
able for ST52x400F/440F/441F devices:
PORT A = 8-bit ports (PA0 - PA7 pins)
PORT B = 5 -bit ports (PB0 - PB3 and PB7 pins)
These I/O lines can be programmed to provide
Digital Input/Output or Analog Input, or to connect
input/output signals to the on-chip peripherals as
Alternate Pin Functions.
The input buffers are TTL compatible with Schmitt
Trigger in ports A and C while port B is CMOS
compatible without Schmitt trigger and it is used
for the Analog Inputs.
The output buffer can supply up to 8 mA.
All the port pins of 400/440 devices have an
internal pull-up resistor (22 kΩ). The 441 device
doesn’t have internal pull-up resistor. This
pull-up resistor is automatically excluded
when the pin is configured as Analog Input or,
in MAIN1 and MAIN2 pins, when the Triac
Driver is configured in Phase Angle Partializa-
tion or Burst mode.
Each single port pin can be programmed in input
or output or Alternate Function, so that in the
same port there can be both input and output pins.
The port pins are write/read in parallel at the same
time: when reading output pins, the port buffer
contents are read; when writing an input pin the
value is written in the buffer.
Each port is configured by using Configuration
Registers indicated in Table 6.1. The first is used
to define if a pin is an Input or an Output, the sec-
ond defines the Alternate functions.
Table 6.1 I/O Port Configuration Register
PORT A
Reg_Conf 4
Reg_Conf 12
PORT B
Reg_Conf 13
Reg_Conf 14
Reg_Conf 11**
PORT C (*)
Reg_Conf 11
(*) Not available in ST52x400F/440F/441F
(**) Only in ST52x440F/441F
Figure 6.1 Ports A and C Functional Blocks
Vcc
TO INPUT REGISTER
and PERIPHERALS
22 k
TTL
PORT A PIN
or PORT C PIN
FROM PERIPHERAL
FROM OUTPUT REGISTER
FROM CONFIGURATION REGISTER
FROM CONFIGURATION REGISTER
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