AT83C51RB2-3CSCM View Datasheet(PDF) - Atmel Corporation
Part Name
Description
Manufacturer
AT83C51RB2-3CSCM Datasheet PDF : 83 Pages
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AT80C51RD2/AT83C51Rx2
Keyboard Interface
Interrupt
The T8xc51Rx2 implement a keyboard interface allowing the connection of a 8 x n
matrix keyboard. It is based on 8 inputs with programmable interrupt capability on both
high or low level. These inputs are available as alternate function of P1 and allow to exit
from idle and power-down modes.
The keyboard interfaces with the C51 core through 3 special function registers: KBLS,
the Keyboard Level Selection register (Table 42), KBE, The Keyboard Interrupt Enable
register (Table 41), and KBF, the Keyboard Flag register (Table 40).
The keyboard inputs are considered as 8 independent interrupt sources sharing the
same interrupt vector. An interrupt enable bit (KBD in IE1) allows global enable or dis-
able of the keyboard interrupt (see Figure 20). As detailed in Figure 21 each keyboard
input has the capability to detect a programmable level according to KBLS.x bit value.
Level detection is then reported in interrupt flags KBF.x that can be masked by software
using KBE.x bits.
This structure allow keyboard arrangement from 1 x n to 8 x n matrix and allows usage
of P1 inputs for other purpose.
Figure 20. Keyboard Interface Block Diagram
P1:x
VCC
0
1
Internal Pull-up KBLS.x
KBF.x
KBE.x
Figure 21. Keyboard Input Circuitry
Power Reduction Mode
P1.0
P1.1
P1.2
P1.3
P1.4
P1.5
P1.6
P1.7
Input Circuitry
Input Circuitry
Input Circuitry
Input Circuitry
Input Circuitry
Input Circuitry
Input Circuitry
Input Circuitry
KBD
IE1
KBDIT
Keyboard Interface
Interrupt Request
P1 inputs allow exit from idle and power-down modes as detailed in Section “Power-
down Mode”, page 59.
55
4113B–8051–03/05
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