UPSD3233 STMicroelectronics, UPSD3233 Datasheet - Page 129

• Manufacturer Part Number: UPSD3233
• Description: Flash Programmable System Devices with 8032 Microcontroller Core
• Manufacturer: STMicroelectronics

Port Configuration Registers (PCR)
Each Port has a set of Port Configuration Regis-
ters (PCR) used for configuration. The contents of
the registers can be accessed by the MCU through
normal READ/WRITE bus cycles at the addresses
given in Table 84. The addresses in Table 84 are
the offsets in hexadecimal from the base of the
CSIOP register.
The pins of a port are individually configurable and
each bit in the register controls its respective pin.
For example, Bit 0 in a register refers to Bit 0 of its
port. The three Port Configuration Registers
(PCR), shown in Table 95, are used for setting the
Port configurations. The default Power-up state for
each register in Table 95 is 00h.
Control Register. Any bit reset to '0' in the Con-
trol Register sets the corresponding port pin to
MCU I/O Mode, and a '1' sets it to Address Out
Mode. The default mode is MCU I/O. Only Ports A
and B have an associated Control Register.
Direction Register. The Direction Register, in
conjunction with the output enable (except for Port
D), controls the direction of data flow in the I/O
Ports. Any bit set to '1' in the Direction Register
causes the corresponding pin to be an output, and
any bit set to '0' causes it to be an input. The de-
fault mode for all port pins is input.
Figure 65, page 131 and Figure 66, page 132
show the Port Architecture diagrams for Ports A/B
and C, respectively. The direction of data flow for
Ports A, B, and C are controlled not only by the di-
rection register, but also by the output enable
product term from the PLD AND Array. If the out-
put enable product term is not active, the Direction
Register has sole control of a given pin’s direction.
An example of a configuration for a Port with the
three least significant bits set to output and the re-
mainder set to input is shown in Table 98. Since
Port D only contains two pins (shown in Figure 68),
the Direction Register for Port D has only two bits
active.
Drive Select Register. The Drive Select Register
configures the pin driver as Open Drain or CMOS
for some port pins, and controls the slew rate for
the other port pins. An external pull-up resistor
should be used for pins configured as Open Drain.
A pin can be configured as Open Drain if its corre-
sponding bit in the Drive Select Register is set to a
'1.' The default pin drive is CMOS.
UPSD3234A, UPSD3234BV, UPSD3233B, UPSD3233BV
Note: The slew rate is a measurement of the rise
and fall times of an output. A higher slew rate
means a faster output response and may create
more electrical noise. A pin operates in a high slew
rate when the corresponding bit in the Drive Reg-
ister is set to '1.' The default rate is slow slew.
Table 99, page 130 shows the Drive Register for
Ports A, B, C, and D. It summarizes which pins can
be configured as Open Drain outputs and which
pins the slew rate can be set for.
Table 95. Port Configuration Registers (PCR)
Note: 1. See Table 99 for Drive Register Bit definition.
Table 96. Port Pin Direction Control, Output
Enable P.T. Not Defined
Table 97. Port Pin Direction Control, Output
Enable P.T. Defined
Table 98. Port Direction Assignment Example
Control
Direction
Drive Select
0
1
0
0
1
1
0
Bit 7
Register Name
Direction Register Bit
Register Bit
Direction
Bit 6
0
(1)
0
Bit 5
A,B
A,B,C,D
A,B,C,D
0
1
0
1
Output Enable
Bit 4
0
Port
P.T.
Input
Output
0
Bit 3
Port Pin Mode
Bit 2
1
WRITE/READ
WRITE/READ
WRITE/READ
Input
Output
Output
Output
Port Pin Mode
MCU Access
1
Bit 1
129/175
1
Bit 0