UPSD325X datasheet(131/176 Pages) STMICROELECTRONICS

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µPSD325X DEVICES

Port Data Registers

The Port Data Registers, shown in Table 100, are

used by the MCU to write data to or read data from

the ports. Table 100 shows the register name, the

ports having each register type, and MCU access

for each register type. The registers are described

below.

Data In. Port pins are connected directly to the

Data In buffer. In MCU I/O Input Mode, the pin in-

put is read through the Data In buffer.

Data Out Register. Stores output data written by

the MCU in the MCU I/O Output Mode. The con-

tents of the Register are driven out to the pins if the

Direction Register or the output enable product

term is set to ’1.’ The contents of the register can

also be read back by the MCU.

Output Macrocells (OMC). The

CPLD

Output

Macrocells (OMC) occupy a location in the MCU’s

address space. The MCU can read the output of

the Output Macrocells (OMC). If the OMC Mask

loads data to the macrocell flip-flops. See the sec-

tion entitled “PLDs,” page 120.

OMC Mask Register. Each OMC Mask Register

Bit corresponds to an Output Macrocell (OMC) flip-

flop. When the OMC Mask Register Bit is set to a

'1,' loading data into the Output Macrocell (OMC)

flip-flop is blocked. The default value is '0' or un-

blocked.

Input Macrocells (IMC). The

Input Macrocells

(IMC) can be used to latch or store external inputs.

The outputs of the Input Macrocells (IMC) are rout-

ed to the PLD input bus, and can be read by the

MCU. See the section entitled “PLDs,” page 120.

Enable Out. The Enable Out register can be read

by the MCU. It contains the output enable values

for a given port. A '1' indicates the driver is in out-

put mode. A '0' indicates the driver is in tri-state

and the pin is in input mode.

Table 99. Drive Register Pin Assignment

Note: 1. NA = Not Applicable.

Table 100. Port Data Registers

Drive

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

Port A

Open

Drain

Open

Drain

Open

Drain

Open

Drain

Slew

Rate

Slew

Rate

Slew

Rate

Slew

Rate

Port B

Open

Drain

Open

Drain

Open

Drain

Open

Drain

Slew

Rate

Slew

Rate

Slew

Rate

Slew

Rate

Port C

Open

Drain

Open

Drain

Open

Drain

Open

Drain

Open

Drain

Open

Drain

Open

Drain

Open

Drain

Port D

NA1

Slew

Rate

Slew

Rate

NA1

Port

MCU Access

Data In

A,B,C,D

READ – input on pin

Data Out

A,B,C,D

WRITE/READ

Output Macrocell

A,B,C

READ – outputs of macrocells

WRITE – loading macrocells flip-flop

Mask Macrocell

A,B,C

WRITE/READ – prevents loading into a given

macrocell

Input Macrocell

A,B,C

READ – outputs of the Input Macrocells

Enable Out

A,B,C

READ – the output enable control of the port driver

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