8

83C51KB HIGH PERFORMANCE KEYBOARD MICROCONTROLLER

Table 6. 83C51KB Signal Description

Signal

Name

Type

Description

Alternate

Function

O

Address Signals . Upper address lines for the external bus. These

signals are normally used for the KSO15:8 scan function and are not

available for external memory access in a keyboard application. (See

KSO signals).

KSO.15:8

P2.15:8

I/O

Address/Data Signals. Multiplexed lower address and data signals

for external memory. These signals are normally used for the KSO7:0

scan function and are not available for external memory access in a

keyboard application. (See KSO)

KSO.7:0

P0.7:0

O

Address Latch Enable. ALE signals the start of an external bus cycle

and indicates that valid address information is available on lines A15:8

and AD7:0. Since these external address signals are normally used for

the KSO scan function, the ALE should not be used for external mem-

ory access in a keyboard application. ALE can be disabled when not

used for external memory access by setting bit 0 of SFR AUXR at

address 8EH.

CLK1:0

P3.3:2

I/O

Clock signal. Either P3.2 or P3.3 is configurable with a 1.8K

Ω pullup

and with external interrupt INT0# or INT1# and used as keyboard CLK

signal.

INT1:0#

DATA

P3.0

I/O

DATA signal. P3.0 is configurable with a 1.8K

Ω pullup and used as key-

board Data signal..

EA#

I

External Access. Directs program memory accesses to on-chip or off-

chip code memory. For EA# = 0, all program memory accesses are off-

using the 83C51KB.

I

External Interrupts 0 and 1. These inputs set bits IE1:0 in the TCON

register. If bits IT1:0 in the TCON register are set, bits IE1:0 are set by

a falling edge on INT1#/INT0#. If bits INT1:0 are clear, bits IE1:0 are

set by a low level on INT1:0#. For keyboard applicaitons, these signals

are normally used for the CLK signals. (See KSIINT and CDPU bits in

the PCON register)

CLK1:0

P3.3:2

KSI7:0

P1.7:0

I/O

Keyboard Scan Inputs. Application specific keyboard signals.

KSO15:0

P2.15:8

P0.7:0

I/O

Keyboard Scan Outputs. The KSO signals are application specific to

keyboard scan functions.

LED3:0

P3.7:4

I/O

Light Emitting Diode Drivers. The LED signals are specifically designed to

drive LEDs connected to Vcc directly (see D.C. Characteristics). The

alternate functions are not available for keyboard applications.

RD#, WR#,

T0

N/C

—

No Connection Signal. This signal is to be unconnected.

I/O

Port 0. This is an 8-bit quasi-bidirectional I/O port (see KSO signals,

see also AD7:0).

AD7:0

P1.7:0

I/O

Port 1. This is an 8-bit quasi-bidirectional I/O port (see KSI signals).

P2.7:0

I/O

Port 2. This is an 8-bit quasi-bidirectional I/O port (see also A15:8).

A15:8

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