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5–9
5.10.1
Normal Mode (CB = 1)
When the chip is configured as a continuous transmitter (CA = 1, CF = CG = CH = 0, and CC = 1), as a
triggered transmitter (CA = 1, CF = CG = CH = 0, and CC = 0, CI = 1), or as a periodic transmitter
(CA = 1, CF = CG = CH = 0, and CC = 0, CI = 0), and EEPROM bit CB is set to 1, the TMS3637 operates
as a normal transmitter and emits the stored code on OUT (the open drain requires a pullup resistor). The
format for the code appearing on OUT is:
•
Each code transmission consists of a 3-bit precode (010) or sync word followed by 22 data bits
(C1 through C22) stored in the EEPROM.
•
A bit code 1 is represented high with a duration of t
1
, and a bit code 0 is represented high with
a duration of t
2
= 7 t
1
.
An example of OUT is shown in Figure 5–4.
Precode (3 bits)
t2
t1
OUT
Security Code (22 bits)
0
0
0
1
0
0
1
1
0
1
1
0
1
1
C01
C02
C03
C04
C22
Figure 5–4. OUT Waveform in Normal Transmission
5.10.2
Modulated Mode (CB = 0)
When the chip is configured as a continuous transmitter (CA = 1, CF = CG = CH = 0, and CC = 1), as a
triggered transmitter (CA = 1, CF = CG = CH = 0, and CC = 0, CI = 1), or as a periodic transmitter (CA = 1,
CF = CG = CH = 0, and CC = 0, CI = 0), and EEPROM bit CB clears to 0, the device is programmed to
function as a modulated transmitter. The oscillator frequency must be 120 kHz.
In the modulated mode, a bit code 1 is represented high with a pulse width of t
3
= t
4
. A bit code 0 is
represented by a high of t
0
= 7 t
4
as in the normal mode, except that the bit codes are each separated by
a pulse train composed of five elementary pulses. The total duration of t
4
= 125
µ
s as shown in Figure 5–5.
25
µ
s
t4 = 125
µ
s
t3
Bit Code 1
t0 = 7 t4
Bit Code 0
Figure 5–5. OUT Waveform in Modulated Mode
5.10.3
Code-Train Mode (CD, CE)
When the chip is configured as a triggered transmitter (CA = 1, CF = CG = CH = 0, and CC = 0,
CI = 1) or as a periodic transmitter (CA = 1, CF = CG = CH = 0 and CC = 0, CI = 0), it can transmit
the stored code two, four, or eight times, depending on the values stored in bits CD and CE as shown
in Table 5–5 and Figure 5–6.
Summary of Contents for TMS3637
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