SAA3008U/N1 データシートの表示（PDF） - Philips Electronics

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SAA3008U/N1

Infrared remote control transmitter(RECS 80 low voltage)

Philips Electronics 

Philips Semiconductors

Infrared remote control transmitter

(RECS 80 low voltage)

Preliminary specification

SAA3008

FUNCTIONAL DESCRIPTION

Key matrix (DRV0N -DRV6N and SEN0N-SEN6N)

The transmitter keyboard is arranged as a scanned matrix

with seven driver outputs (DRV0N to DRV6N) and seven

sensing inputs (SEN0N to SEN6N) as shown in Fig.1.

The driver outputs are open-drain n-channel transistors

which are conductive in the stand-by mode. The sensing

inputs enable the generation of 56 command codes. With

two external diodes connected (or triple contact), as in

Fig.1, all 64 commands are addressable. The sense lines

have p-channel pull-up transistors, so that they are HIGH

until pulled LOW by connecting them to an output via a key

depression to initiate a code transmission.

The maximum allowable value of contact series resistance

for keyboard switches in the ON-state is 7 kΩ.

Address/mode input (ADRM)

Subsystem addresses are defined by connecting one or

two of the key matrix driver lines (DRV0N to DRV6N) to the

ADRM input. This allows up to 20 subsystem addresses to

be generated for the REMO output (bits S3, S2, S1 and

S0) as shown in Table 1 and Fig.3.

The transmission mode is defined by the DRV6N to ADRM

connection as follows:

• Mode 1 DRV6N not connected to ADRM

• Mode 2 DRV6N connected to ADRM

In Mode 1 the reference time REF equals 3To, this may be

used as a reference time for the decoding sequence.

In Mode 2 an additional modulated pulse has been

inserted into the middle of the reference time, therefore,

these pulses are now separated by 1.5To. This unique

start pattern START uses the detection of a beginning

word (see Fig.3).

When more than one connection is made to ADRM then all

connections should be decoupled using diodes.

The ADRM input has switched pull-up and pull-down

loads. In the stand-by mode only pull-down load is active

and ADRM input is held LOW (this condition is

independent of the ADRM circuit configuration and

minimizes power loss in the standby mode). When a key is

pressed the transmitter becomes active pull-down is

switched OFF, pull-up is switched ON) and the driver line

signals are sensed for the subsystem address coding.

The subsystem address is sensed only within the first scan

cycle, whereas the command code is sensed in every

scan. The transmitted subsystem address remains

unchanged if the subsystem address selection is changed

while the command key is pressed. A chance of the

subsystem address does not start a transmission.

In a multiple keystroke sequence (Fig.6) the second

word B might be transmitted with subsystem address 18 or

19 instead of the preselected subsystem address

(Table 1). This is only relevant for systems decoding

subsystem address 18 or 19.

Remote control signal output (REMO)

The REMO output driver stage incorporates a bipolar

emitter-follower which allows a high output current in the

output active (HIGH) state (Fig.7).

The information is defined by the distance ‘tb’ between the

leading edges of the modulated pulses (Fig.4). The

distance tb is a multiple of the basic unit To (Table 3) which

equals 1152 periods of the oscillator frequency fosc

(Table 3). The pulses are modulated with 6 periods of 1⁄12

of the oscillator frequency (38 kHz).

The format of the output data is illustrated in Figs 3 and 4.

A data word starts with the reference time and toggle bit T0

and is followed by the definition bits for the subsystem

address S3, S2, S1 and S0 (bit S3 is transmitted only for

subsystem addresses 8 to 20).

The selected command key is defined by bits F, E, D, C, B

and A as shown in Table 2.

The toggle bit T0 acts as an indication for the decoder

whether the next instruction should be considered as a

new command or not. The codes for the subsystem

address and the selected key are given in Table 3.

December 1988

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