9

83C51KB HIGH PERFORMANCE KEYBOARD MICROCONTROLLER

P3.7:0

I/O

Port 3. This is an 8-bit quasi-bidirectional I/O port (see CLK1:0, DATA,

LED3:0).

O

Program Store Enable. This output is asserted for external program

memory fetch operations. It is not available for keyboard applications.

—

RCIN

I

Resonant Clock Input. RC resonator generated by connecting 1% preci-

clock device.

O

Read . Read signal output for external data memory read operations.

It is not available for keyboard applications.

LED3

RST

I

Reset. Asserting RST when the chip is in idle mode or powerdown

mode returns the chip to normal operation. This signal is input only.

When power is applied to the chip, the internal reset signal remains

high for approximately 80ms to 260ms (see the datasheet for current

specifications). The reset circuit then deactivates and does not re-

3VDC.

—

PWR

Supply Voltage. Connect this pin to the +5V supply voltage.

—

GND

Circuit Ground. Connect this pin to ground.

—

O

Write. Write signal output for external data memory write operations.

It is not available for keyboard applications.

LED2

Table 6. 83C51KB Signal Description

Signal

Name

Type

Description

Alternate

Function

standard MCS 51 microcontrollers. They are not used for these functions in keyboard applications.