Motorola DSP56301 user manual Direction, Timer Reload Mode, Inverter

Models: DSP56301

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Triple Timer Module Programming Model

Table 9-3.Timer Control/Status Register (TCSR) Bit Definitions (Continued)

Bit Number

Bit Name

Reset Value

Description

 

 

 

 

 

 

 

 

11

DIR

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.

 

 

 

 

10

 

0

Reserved. Write to zero for future compatibility.

 

 

 

 

9

TRM

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.

 

 

 

 

8

INV

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.

 

 

 

 

9-30

DSP56301 User’s Manual

Page 292
Image 292
Motorola DSP56301 user manual Direction, Timer Reload Mode, Inverter