saa3008 NXP Semiconductors, saa3008 Datasheet - Page 9

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

Philips Semiconductors
Table 3 Pulse timing
OPERATION
Keyboard
In the standby mode all drivers DRV0N-DRV6N are ON
but are non-conducting due to their open drain
configuration. When a key is pressed, a completed drain
connection pulls down one or more of the sense lines to
ground. Referring to Fig.5, the power-up sequence for the
IC commences as a key is pressed. The oscillator
becomes active and then, following the debounce time
(t
Within the first scan cycle the transmission mode,
subsystem address and the selected command code are
sensed and loaded into an internal data latch. In a multiple
keystroke sequence (Fig.6) the command code is always
altered according to the sensed key.
Multiple keystroke protection
The keyboard is protected against multiple keystrokes.
If more than one key is pressed the circuit will not generate
a new REMO sequence (Fig.6).
In a multiple keystroke sequence the scan repetition rate
is increased to detect the release of the key as soon as
possible.
December 1988
Modulation period
Modulation LOW time
Modulation HIGH time
Modulation pulse width
Basic unit of pulse spacing
Word length for subsystem
Pulse separation for
Start pattern
DB
Infrared remote control transmitter
(RECS 80 low voltage)
addresses
0 to 7
8 to 20
logic 0
logic 1
reference time
toggle bit
), the output drivers become active successively.
PARAMETER
t
t
t
t
t
t
t
t
t
t
t
t
M
ML
MH
PW
o
W
W
b
b
b
b
b
SYMBOL
9
There are two restrictions caused by the special structure
of the keyboard matrix:
Output sequence
The output operation starts when the code of the selected
key has been loaded into the internal command register.
A burst of pulses, including the latched address and
command codes, is generated at the output REMO for as
long as the key is pressed. The format of the output pulse
train is as shown in Figs 3 and 4. The operation is
terminated by releasing the key, or by pressing more than
one key at the same time. Once a sequence has been
started, the transmitted words will always be completed
after the key has been released.
The toggle bit T0 is incremented if the key is released for
a minimum time t
sequence the toggle bit remains unchanged.
The keys switching directly to ground (codes 7, 15, 23,
31, 39, 47, 55, 63) are not completely covered by
multiple keystroke protection. If one sense input is
switched to ground, other keys on that sense line are
ignored.
The sense lines SEN5N and SEN6N are not protected
against multiple keystrokes on the same driver line
because this has been used to define codes 56 to 63.
12t
8t
4t
5t
1152t
55296t
59904t
2t
3t
3t
2t
3t
2
DURATION
M
osc
osc
o
o
o
o
o
osc
1.5t
osc
t
MH
osc
osc
o
REL
(Fig.5). In a multiple keystroke
DURATION at f
121.44 ms
132.56 ms
140.8
26.4
17.6
2.53 ms
5.06 ms
7.59 ms
7.59 ms
5.06 ms
7.59 ms
t
2
OSC
Preliminary specification
8.8
3.79 ms
= 2.2 s
OSC
s
s
s
s
SAA3008
= 455 kHz;