PC87373 datasheet(73/174 Pages) NSC

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Revision 1.1

5.0

General-Purpose Input/Output (GPIO) Ports

This chapter describes one 8-bit port. A device may include a combination of several ports with different implementations.

For device specific implementation, see Section 3.14 on page 62.

5.1 OVERVIEW

The GPIO port is an 8-bit port, connected to eight pins. It features:

• Software capability to control and read pin levels.

• Flexible system notification by several means, based on the pin level or level transition.

• Ability to capture and route events and their associated status.

• Back-drive protected pins.

GPIO port operation is associated with two sets of registers:

• Pin Configuration registers mapped in the Device Configuration space. These registers are used to configure the logical

behavior of each pin. There are three registers for each GPIO pin: GPIO Pin Configuration registers 1 and 2 (GPCFG1,

GPCFG2) and the GPIO Pin Event Routing register (GPEVR).

• Four 8-bit runtime registers: GPIO Data Out (GPDO), GPIO Data In (GPDI), GPIO Event Enable (GPEVEN) and GPIO

Event Status (GPEVST). These registers are mapped in the GPIO device I/O space (which is determined by the base

address registers in the GPIO Device Configuration). They are used to control and/or read the pin values and to handle

system notification. Each runtime register corresponds to the 8-pin port, such that bit ‘n’ in each one of the four registers

is associated with GPIOXn pin, where ‘X’ is the port number.

• An additional optional runtime register: GPIO Data In/Out (GPDIO). This register is also mapped in the GPIO device I/O

space, but at a separate location from the above group of four runtime registers. It contains the same data-out value as

the GPDO register and the same data-in value as the GPDI register.

Each GPIO pin is associated with configuration bits and the corresponding bit slice of the four runtime registers, as shown

in Figure 9.

Figure 9. GPIO Port Architecture

GPIO Pin

Select (GPSEL)

Conﬁguration 1 and 2

GPDOX

GPDIX

GPEVENX

GPEVSTX

Runtime

Registers

GPIOX Base Address

Event

Bit n

Port and Pin

8 GPCFG

Registers

GPIOXn

GPIOXn CNFG

Interrupt Request

GPIOXn

Port Logic

X = port number

n = pin number (0 to 7)

Pending

Indication

GPIO Pin Event

Routing (GPEVR)

8 GPEVR

Registers

GPIOXn ROUTE

Select

Event

Routing

Control

Registers

(GPCFG1 and GPCFG2)

SWC

SIOPME

GPIO

GPDIOX

PC87373 Datasheet(PDF) 73 Page - National Semiconductor (TI)

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