AT89C5131A-M Atmel Corporation, AT89C5131A-M Datasheet - Page 88

• Manufacturer Part Number: AT89C5131A-M
• Manufacturer: Atmel Corporation

Specifications of AT89C5131A-M

• Flash (kbytes): 32 Kbytes
• Max. Operating Frequency: 48 MHz
• Cpu: 8051-12C
• Max I/o Pins: 34
• Usb Transceiver: 1
• Usb Speed: Full Speed
• Usb Interface: Device
• Spi: 1
• Twi (i2c): 1
• Uart: 1
• Sram (kbytes): 1.25
• Eeprom (bytes): 1024
• Self Program Memory: API
• Operating Voltage (vcc): 2.7 to 5.5
• Timers: 4
• Isp: UART/USB
• Watchdog: Yes

17. Keyboard Interface
17.1
17.2
17.2.1
88
Introduction
Description
AT89C5130A/31A-M
Interrupt
The AT89C5130A/31A-M implements 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 an alternate function of P1 and allow to exit from idle
and power down modes.
The keyboard interface communicates with the C51 core through 3 special function registers:
KBLS, the Keyboard Level Selection register (Table 17-3), KBE, The Keyboard interrupt Enable
register (Table 17-2), and KBF, the Keyboard Flag register (Table 17-1).
The keyboard inputs are considered as 8 independent interrupt sources sharing the same inter-
rupt vector. An interrupt enable bit (KBD in IE1) allows global enable or disable of the keyboard
interrupt (see Figure 17-1). As detailed in Figure 17-2 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 by n to 8 by n matrix and allow usage of P1
inputs for other purpose.
Figure 17-1. Keyboard Interface Block Diagram
Figure 17-2. Keyboard Input Circuitry
P1.0
P1.1
P1.2
P1.3
P1.4
P1.5
P1.6
P1.7
P1:x
Input Circuitry
Input Circuitry
Input Circuitry
Input Circuitry
Input Circuitry
Input Circuitry
Input Circuitry
Input Circuitry
Vcc
Internal Pull-up
KBLS.x
0
1
KBF.x
KBD
IE1.0
KBE.x
Keyboard Interface
Interrupt Request
KBDIT
4337K–USB–04/08