T48C893 Datasheet, PDF (48/82 Pages) ATMEL Corporation – The multiple times programmable (MTP) version for the MARC4 ROM types

T48C893
Timer 3 – Mode 12: Timer / counter with external capture mode (T3I)
The counter is driven by an internal clock source and an edge at the external input T3I loads the counter value into the
capture register. The edge can be selected with the programmable edge detector of the timer input stage. This mode
can be used for signal and pulse measurements.
T3R
T3I
Counter 3
T3CP–
Register
0 0 1 2 3 4 5 6 7 8 9 1011121314151617181920212223242526272829303132333435363738394041
Capture value = X
Capture value = 17
Capture
value = 35
13819
Figure 55. External capture mode
Timer 3 Modulator for Carrier Frequency Burst Modulation
If the output stage operates as pulse-width modulator for the shift register the output can be stopped with stage 1 of
Timer 2. For this task, the timer mode 3 must be used and the prescaler must be supplied by the internal shift clock
of the shift register.
The modulator can be started with the start of the shift register (SIR=0) and stopped either by a shift register stop
(SIR=1) or compare match event of stage 1 of Timer 2. For this task, the Timer 2 must be used in mode 3 and the pre-
scaler stage must be supplied by the internal shift clock of the shift register.
TOG3
SO
M2
SSI/
Control
0
T3 M3
1
Set Res
T3TOP
2 _MUX
T3O
3
Timer 3 Mode T3O
6
7
9
other
MUX 1
MUX 2
MUX 3
MUX 0
OMSK
T3M
13820
Figure 56. Modulator 3
Timer 3 Demodulator for Biphase, Manchester and Pulse-Width-Modulated Signals
The demodulator stage of Timer 3 can be used to decode Biphase, Manchester and pulse-width-coded signals
T3M
T3I
SCI
Demodulator 3
SI
T3EX
Res
CM31 Counter 3
Reset
Counter 3
Control
13821
Figure 57. Timer 3 demodulator 3
48 (82)
Rev. A4, 22-Jan-02