CP3UB26 datasheet(67/268 Pages) NSC

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14.0 Input/Output Ports

Each device has up to 54 software-configurable I/O pins, or-

ganized into 8-bit ports (not all bits are used in some ports).

The ports are named Port B, Port C, Port E, Port F, Port G,

Port H, and Port J.

In addition to their general-purpose I/O capability, the I/O

pins of Ports E, F, G, H, and J have alternate functions for

use with on-chip peripheral modules such as the UART or

the Multi-Input Wake-Up unit. The alternate functions of all

I/O pins are shown in Table 91.

Ports B and C are used as the 16-bit data bus when an ex-

ternal bus is enabled (144-pin devices only). This alternate

function is selected by enabling the DEV or ERE operating

environments, not by programming the port registers.

The I/O pin characteristics are fully programmable. Each pin

can be configured to operate as a TRI-STATE output, push-

pull output, weak pull-up input, or high-impedance input.

Different pins within the same port can be individually con-

figured to operate in different modes.

Figure 10 is a diagram showing the I/O port pin logic. The

be configured into the various operating modes. The output

buffer is a TRI-STATE buffer with weak pull-up capability.

The weak pull-up, if used, prevents the port pin from going

to an undefined state when it operates as an input.

To reduce power consumption, input buffers configured for

general-purpose I/O are only enabled when they are read.

When configured for an alternate function, the input buffers

are enabled continuously. To minimize power consumption,

input signals to enabled buffers must be held within 0.2 volts

of the VCC or GND voltage.

The electrical characteristics and drive capabilities of the in-

put and output buffers are described in Section 29.0.

Figure 10.

I/O Port Pin Logic

14.1

PORT REGISTERS

Each port has an associated set of memory-mapped regis-

ters used for controlling the port and for holding the port da-

ta:

PxALT: Port alternate function register

PxALTS: Port alternate function select register

PxDIR: Port direction register

PxDIN: Port data input register

PxDOUT: Port data output register

PxWPU: Port weak pull-up register

PxHDRV: Port high drive strength register

Data In Read Strobe

Alt. A Device Direction

Alt. B Device Direction

Alt. B Data Input

Analog Input

PxDIN Register

PxALTS Register

PxALT Register

PxWKPU Register

PxDIR Register

Alt. A Device Data Outout

Alt. B Device Data Outout

PxDOUT Register

DS190

Alt. A Data Input

VCC

Weak Pull-Up Enable

Output Enable

Data Out

Data In

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