UPSD3212A Datasheet, PDF (116/163 Pages) STMicroelectronics – Flash Programmable System Devices with 8032 MCU with USB and Programmable Logic

uPSD3212A, uPSD3212C, uPSD3212CV
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 81., page 92. The addresses in Ta-
ble 81 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 92, are used for setting the
Port configurations. The default Power-up state for
each register in Table 92 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 61., page 118 and Figure 62., page 119
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 95. Since
Port D only contains two pins (shown in Figure
64., page 121), 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.
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 96., page 117 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 92. Port Configuration Registers (PCR)
Register Name
Port
MCU Access
Control
A,B
WRITE/READ
Direction
A,B,C,D
WRITE/READ
Drive Select^{(1) A,B,C,D}
WRITE/READ
Note: 1. See Table 96., page 117 for Drive Register Bit definition.
Table 93. Port Pin Direction Control, Output
Enable P.T. Not Defined
Direction Register Bit
Port Pin Mode
0
Input
1
Output
Table 94. Port Pin Direction Control, Output
Enable P.T. Defined
Direction
Register Bit
Output Enable
P.T.
Port Pin Mode
0
0
Input
0
1
Output
1
0
Output
1
1
Output
Table 95. Port Direction Assignment Example
Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
0
0
0
0
0
1
1
1
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