17

ATSAM9753

1774D–DRMSD–11/02

Keyboard Configuration

Register

The configuration register allows the user to work with a variety of keyboards. This write-

only 2-bit register is mapped to the address OBH in the I/O space.

Reg[0] = contact type

0 for rubber type contact

1 for spring type contact

Reg[1] = diode wiring

0 for common anode wiring

1 for common cathode wiring

The default configuration (power-up) is common anode (Reg[1] = 0) and rubber contact

(Reg[0] = 0) which corresponds to most popular keyboards.

Scanning Interface

The ATSAM9753 has built-in specialized hardware that allows the following functions:

•

Scanning of up to 88 keys from an external keyboard, with key-on and key-off

velocity measurement (time between contacts)

•

Scanning of up to 176 switches

•

Time multiplex control of up to 88 LEDs

•

Analog-to-digital conversion of up to 16 analog sources

The P16 interfaces with the scanning using a three-address port located at 0CH to 0EH

in the I/O mapping.

This port enables access to the keyboard RAM. This 128 x 11 RAM is mapped as

shown in Table 13.

Keyboard Status

(I/O address OCH read-only)

D[7] KRQ flag = 1 indicates that a key-on or key-off has been detected and that the P16

service is requested. This flag is automatically cleared by writing to data H for the

detected key.

Table 12. LCD Interface

I/O Access

I/O Data

LCD_Reg[10:0]

DB[7:0]

R/W

Write

IOD[10:0]

(IOD[9]=0)

IOD[10:0]

LCD_Reg[9]=0

IOD[7:0] output

0

Set LCD in write mode

Write

IOD[10:0]

(IOD[9]=1)

IOD[10:0]

LCD_Reg[9]=1

LCD_D[7:0] input

1

Set LCD in read mode

Read

xx

LCD_Reg[9]=0

LCD_Reg[7:0] output

0

Invalid read from LCD in write mode

Read

xxx,

LCD_D[7:0]

LCD_Reg[9]=1

LCD_D[7:0] input

1

Read from LCD

Table 13. Keyboard RAM Mapping

Address

Content

00H to 57H

Key velocity and status

58H to 5FH

LED data

60H to 6FH

Switch status

70H to 7FH

ADC value