Motorola DSP56303 User Manual page 242

Triple Timer Module Programming Model
Table 9-3. Timer Control/Status Register (TCSR) Bit Definitions (Continued)
Bit Number Bit Name
11 DIR
10
9 TRM
8 INV
9-30
Reset Value
0 Direction
Determines the behavior of the TIO signal when it functions as a GPIO
signal. When DIR is set, the TIO signal is an output; when DIR is cleared,
the TIO signal is an input. The TIO signal functions as a GPIO signal only
when the TC[3–0] bits are cleared. If any of the TC[3–0] bits are set, then
the GPIO function is disabled, and the DIR bit has no effect.
0 Reserved. Write to zero for future compatibility.
0 Timer Reload Mode
Controls the counter preload operation. In timer (0–3) and watchdog
(9–10) modes, the counter is preloaded with the TLR value after the
TCSR[TE] bit is set and the first internal or external clock signal is
received. If the TRM bit is set, the counter is reloaded each time after it
reaches the value contained by the TCR. In PWM mode (7), the counter is
reloaded each time counter overflow occurs. In measurement (4–5)
modes, if the TRM and the TCSR[TE] bits are set, the counter is preloaded
with the TLR value on each appropriate edge of the input signal. If the
TRM bit is cleared, the counter operates as a free running counter and is
incremented on each incoming event.
0 Inverter
Affects the polarity definition of the incoming signal on the TIO signal when
TIO is programmed as input. It also affects the polarity of the output pulse
generated on the TIO signal when TIO is programmed as output. See
Table 9-4, "Inverter (INV) Bit Operation," on page 32. The INV bit does not
affect the polarity of the prescaler source when the TIO is input to the
prescaler.
NOTE: The INV bit affects both the timer and GPIO modes of operation.
To ensure correct operation, change this bit only when one or both of the
following conditions is true: the timer is disabled (the TCSR[TE] bit is
cleared). The timer is in GPIO mode.
DSP56303 User's Manual
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