Texas Instruments TMS3637P, Data Manual

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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.