UPSD325X datasheet(126/176 Pages) STMICROELECTRONICS

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µPSD325X DEVICES

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The OMC Mask Register. There is one Mask

Macrocells (OMC). The Mask Registers can be

used to block the loading of data to individual Out-

put Macrocells (OMC). The default value for the

Mask Registers is 00h, which allows loading of the

Output Macrocells (OMC). When a given bit in a

Mask Register is set to a ’1,’ the MCU is blocked

from writing to the associated Output Macrocells

(OMC).

For

example,

suppose

McellAB0-

McellAB3 are being used for a state machine. You

would not want a MCU write to McellAB to over-

write the state machine registers. Therefore, you

would want to load the Mask Register for McellAB

(Mask Macrocell AB) with the value 0Fh.

The Output Enable of the OMC. The

Output

Macrocells (OMC) block can be connected to an I/

O port pin as a PLD output. The output enable of

each port pin driver is controlled by a single prod-

uct term from the AND Array, ORed with the Direc-

tion Register output. The pin is enabled upon

Power-up if no output enable equation is defined

and if the pin is declared as a PLD output in PSD-

soft Express.

If the Output Macrocell (OMC) output is declared

as an internal node and not as a port pin output in

the PSDabel file, the port pin can be used for other

I/O functions. The internal node feedback can be

routed as an input to the AND Array.

Input Macrocells (IMC)

The CPLD has 24 Input Macrocells (IMC), one for

each pin on Ports A, B, and C. The architecture of

the Input Macrocells (IMC) is shown in Figure 62.

The Input Macrocells (IMC) are individually config-

urable, and can be used as a latch, register, or to

pass incoming Port signals prior to driving them

onto the PLD input bus. The outputs of the Input

Macrocells (IMC) can be read by the MCU through

the internal data bus.

The enable for the latch and clock for the register

are driven by a multiplexer whose inputs are a

product term from the CPLD AND Array or the

MCU Address Strobe (ALE). Each product term

output is used to latch or clock four Input Macro-

cells (IMC). Port inputs 3-0 can be controlled by

one product term and 7-4 by another.

Configurations for the Input Macrocells (IMC) are

specified by equations written in PSDsoft (see Ap-

plication Note

AN1171). Outputs of the Input Mac-

rocells (IMC) can be read by the MCU via the IMC

buffer. See the section entitled “I/O PORTS (PSD

MODULE),” page 127.

Figure 62. Input Macrocell

OUTPUT

MACROCELLS BC

AND

MACROCELL AB

FEEDBACK

PORT

DRIVER

I/O PIN

MCU DATA BUS

D [ 7: 0]

DIRECTION

MUX

ALE

LATCH

INPUT MACROCELL

ENABLE (.OE)

D FF

INPUT MACROCELL _ RD

AI06603

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