INA3010

3

FUNCTIONAL DESCRIPTION

Keyboard operation

Every connection of one X-input and one DR-output will be recognized as a legal key

operation and will cause the device to generate the corresponding code. The same applies

to every connection of one Z-input to one DR-output with the7 proviso that SSM must be

LOW. When SSM is HIGH a wired connection must exist between a Z-input and a DR-

output. If no connection is present the system number will not be generated. Activating two

or more X-inputs, Z-inputs or Z-inputs and X-inputs at the same time is an illegal action

and inhibits further activity (oscillator will not start).

When one X- or Z-input is connected to more than one DR-output, the last scan signal will

be considered as legal.

The maximum value of the contact series resistance of the switched keyboard is 7 kW.

Inputs

In the quiescent state the command inputs X0 to X7 are held HIGH by an internal pull-up

transistor. When the system mode selection (SSM) input is LOW and the system is

quiescent, the system inputs Z0 to Z3 are also held HIGH by an internal pull-up transistor.

When SSM is HIGH the pull-up transistor for the Z-inputs is switched off, in order to

prevent current flow, and a wired connection in the Z-DR matrix provides the system

number.

Outputs

The output signal DATA transmits the generated information in accordance with the format

illustrated by Fig.3. The code is transmitted using a biphase technique as illustrated by

Fig.4. The code consists of four parts:

· Start part -1.5 bits (2 ´ logic 1)

· Control part -1 bit

· System part -5 bits

· Command part -6 bits

The output signal MDATA transmits the generated information modulated by 1/12 of the

oscillator frequency with a 50%

duty factor.

In the quiescent state both DATA and MDATA are non-conducting (3-state outputs).

The scan driver outputs DR0 to DR7 are open drain n-channel transistors and conduct

when the circuit is quiescent. After a legal key operation the scanning cycle is started and

the outputs switched to the conductive state one by one. The DR-outputs were switched

off at the end of the preceding debounce cycle.

Command matrix (X-DR)

Code

X-lines

DR-lines

Command bits

no.

0

1

2

3

4

5

6

7

0

1

2

3

4

5

6

7

5

4

3

2

1

0

0

x

x

0

0

0

0

0

0

1

x

x

0

0

0

0

0

1

2

x

x

0

0

0

0

1

0

3

x

x

0

0

0

0

1

1

4

x

x

0

0

0

1

0

0

5

x

x

0

0

0

1

0

1

6

x

x

0

0

0

1

1

0

7

x

x

0

0

0

1

1

1

8

x

x

0

0

1

0

0

0

9

x

x

0

0

1

0

0

1

10

x

x

0

0

1

0

1

0

11

x

x

0

0

1

0

1

1