TC1784
Fast Analog to Digital Converter (FADC)
User´s Manual
24-11
V1.1, 2011-05
FADC, V2.21
24.2.5
Channel Timer
Each of the FADC channels contains an 8-bit Channel Timer that can be used to
generate periodic conversion requests. The Channel Timer is built up by a decrementing
counter that is reloaded with a programmable value. When the Channel Timer reaches
zero while running, a Channel Timer trigger event is generated and the Channel Timer
is reloaded with the reload value CFGRx.CTREL when the requested conversion is
started. With the start of the A/D conversion, request bit CRSR.CRFx is cleared. Note
that the request flag is set by a timer trigger event only if the gating condition is met
(signal ECHTIMx in
set).
A clock divider, fed by the module clock
f
FADC
and common for all Channel Timers,
generates several clock signals with different periods. Bit field CFGRx.CTF selects
whether or not the channel x timer clock
f
CTx
is enabled and, if enabled, determines the
frequency of channel x timer input clock
f
CTx
.
While the Channel Timer is disabled (CFGRx.CTM = 00
B
) or if the gating condition is not
met (gating line ECHTIMx delivers 0), the channel x timer value is set to 04
H
. This value
ensures a fast conversion trigger after the gating becomes enabled, but prevents
unintended conversion starts in case of short pulses (bouncing) at the gating input.
Figure 24-5 Channel Timer Block Diagram
Due to the common divider, the first event at the trigger output of CHTIMx after the start
has a maximum jitter of one clock cycle of the selected channel x timer clock
f
CTx
.
A Channel x Timer input clock pulse at
f
CTx
is ignored if it occurs in the
f
FADC
clock cycle
directly after the Channel x Timer has reached 0. If there is at least one
f
FADC
clock cycle
between two Channel x Timer input clock pulses, all Channel x Timer input clock pulses
MCA06434
Channel Timer
Channel conversion
started and channel
timer is running
CTF
CFGRx
CTREL
Channel x Timer
trigger event
Channel x Timer
enable ECHTIMx
CTM
8
Run Control
Channel x Timer
To other
Channel
Timers
÷ 4
÷ 16
÷ 64
÷ 256
÷ 1024
f
FADC
Clock Divider
for
Channel Timers
f
CTx
0
3
2
Summary of Contents for TC1784
Page 1: ...User s Manual V1 1 2011 05 Microcontrollers TC1784 32 Bit Single Chip Microcontroller ...
Page 3: ...User s Manual V1 1 2011 05 Microcontrollers TC1784 32 Bit Single Chip Microcontroller ...
Page 950: ...TC1784 Direct Memory Access Controller DMA User s Manual 11 132 V1 1 2011 05 DMA V3 03 ...
Page 1949: ...TC1784 General Purpose Timer Array GPTA v5 User s Manual 21 297 V1 1 2011 05 GPTA v5 V1 14 ...
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