COP8TAB9 datasheet(13/59 Pages) NSC

13 / 59 page

8.0 Electrical Characteristics (Continued)

9.0 Pin Descriptions

The COP8TAB9/TAC9 I/O structure enables designers to

reconfigure the microcontroller’s I/O functions with a single

instruction. Each individual I/O pin can be independently

configured as output pin low, output high, input with high

impedance or input with weak pull-up device. A typical ex-

ample is the use of I/O pins as the keyboard matrix input

lines. The input lines can be programmed with internal weak

pull-ups so that the input lines read logic high when the keys

are all open. With a key closure, the corresponding input line

will read a logic zero since the weak pull-up can easily be

overdriven. When the key is released, the internal weak

pull-up will pull the input line back to logic high. This elimi-

nates the need for external pull-up resistors. The high cur-

rent options are available for driving LEDs, motors and

speakers. This flexibility helps to ensure a cleaner design,

with fewer external components and lower costs. Below is

the general description of all available pins.

CC and GND are the power supply pins.

Users of the LLP package are cautioned to be aware that the

central metal area and the pin 1 index mark on the bottom of

the package may be internally connected to GND. See figure

below:

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FIGURE 3. ACB Start Condition Timing

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FIGURE 4. ACB Data Timing

COP8TAB9 Datasheet(PDF) 13 Page - National Semiconductor (TI)