M3004LD

2/14

Figure 3. Block Diagram

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 4.

The driver outputs DRV0N to DRV6N are open

drain N-channel transistors and they are conduc-

tive 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-

odes. This allows the definition 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 connect-

ed to the driver outputs, this input is LOW and will

not cause unwanted dissipation. When the trans-

mitter 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-system ad-

dress 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 sys-

tems requiring more than one sub-system ad-

dress. The transmitter may be hard-wired for

subsystem 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

DRV OUTPUTS

0N 1N 2N 3N 4N 5N 6N

KEYBOARD

SCAN

0N

1N

2N

3N

4N

5N

6N

PULSE

DISTANCE

MODULATOR

CONTROL

LOGIC

OSCILLATOR

OSCI OSCO

REMO

OUTPUT

S

E

N

I

N

P

U

T

S