INPUTS AND OUTPUTS

Key matrix inputs and outputs (DRV0N to

DRV6N and SEN0N to SEN6N)

The transmitter keyboard is arranged as a scanned

matrix. The matrix consists of 7 driver outputs and

7 sense inputs as shown in Figure 1. The driver

outputs DRV0N to DRV6N are open drain N-chan-

nel tran-sistors and they are conductive in the

stand-by mode. The 7 sense inputs (SEN0N to

SEN6N) enable the generation of 56 command

codes. With 2 external diodes all 64 commands are

addressable. The sense inputs have P-channel

pull-up transistors so that they are HIGH until they

are pulled LOW by connecting them to an output

via a key depression to initiate a code transmission.

ADDRESS MODE INPUT (ADRM)

The sub-system address and the transmission

mode are defined by connecting the ADRM input

to one or more driver outputs (DRV0N to DRV6N)

of the key matrix. If more than one driver is con-

nected to ADRM, they must be decoupled by di-

ode s. This allows the defini tion of seven

sub-system addresses as shown in table 3. If driver

DRV6N is connected to ADRM, the data output

format of REMO is modulated or if not connected,

flashed.

The ADRM input has switched pull-up and pull-

down loads. In the stand-by mode only the pull-

down device is active. Whether ADRM is open

(sub-system address 0, flashed mode) or con-

nected to the driver outputs, this input is LOW and

will not cause unwanted dissipation. When the

transmitter becomes active by pressing a key, the

pull-down device is switched off and the pull-up

device is switched on, so that the applied driver

signals are sensed for the decoding of the sub-sys-

tem address and the mode of transmission.

The arrangement of the sub-system address cod-

ing is such that only the driver DRVnM with the

highest number (n) defines the sub-system ad-

dress, e.g. if drivers DRV2N and DRV4N are con-

nected to ADRM, only DRV4N will define the

sub-system address. This option can be used in

systems requiring more than one sub-system ad-

dress. The transmitter may be hard-wired for sub-

system address 2 by connecting DRV1N to ADRM.

If now DRV3N is added to ADRM by a key or a

switch, the transmitted sub-system address

changes to 4. A change of the sub-system address

will not start a transmission.

ADRM

DD

V

OSCILLATOR

KEYBOARD

SCAN

PULSE

DISTANCE

MODULATOR

CONTROL

LOGIC

REMO

OUTPUT

OSCI

OSCO

DRV OUTPUTS

S

E

N

I

N

P

U

T

S

0N 1N

3N 4N 5N 6N

2N

0N

1N

2N

3N

4N

5N

6N

BLOCK DIAGRAM

M3004LAB1 - M3004LD

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