saa3008 NXP Semiconductors, saa3008 Datasheet - Page 4

• Manufacturer Part Number: saa3008
• Description: Infrared Remote Control Transmitter Recs 80 Low Voltage
• Manufacturer: NXP Semiconductors

Philips Semiconductors
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 k .
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:
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
December 1988
Mode 1
Mode 2
Infrared remote control transmitter
(RECS 80 low voltage)
DRV6N not connected to ADRM
DRV6N connected to ADRM
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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 ‘t
leading edges of the modulated pulses (Fig.4). The
distance t
equals 1152 periods of the oscillator frequency f
(Table 3). The pulses are modulated with 6 periods of
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.
b
is a multiple of the basic unit T
Preliminary specification
o
SAA3008
(Table 3) which
b
’ between the
osc
1
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