Motorola DSP56301 - Manual (Page 287)

Triple Timer Module Programming Model
Triple Timer Module 9 -25
9.3.4.3 Reserved Modes
Modes 8, 11, 12, 13, 14, and 15 are reserved.
9.3.5 Special Cases
The following special cases apply during wait and stop state.
n Timer behavior during wait — Timer clocks are active during the execution of the
WAIT instruction and timer activity is undisturbed. If a timer interrupt is generated,
the DSP56301 leaves the wait state and services the interrupt.
n Timer behavior during stop — During execution of the STOP instruction, the timer
clocks are disabled, timer activity stops, and the
TIO signals are disconnected. Any
external changes that happen to the TIO signals are ignored when the DSP56301 is in
stop state. To ensure correct operation, disable the timers before the DSP56301 is
placed in stop state.
9.3.6 DMA Trigger
Each timer can also trigger DMA transfers if a DMA channel is programmed to be triggered
by a timer event. The timer issues a DMA trigger on every event in all modes of operation. To
ensure that all DMA triggers are serviced, provide for the preceding DMA trigger to be
serviced before the DMA channel receives the next trigger.
9.4 Triple Timer Module Programming Model
The timer programmer’s model in Figure 9-20 shows the structure of the timer registers.
9.4.1 Prescaler Counter
The prescaler counter is a 21-bit counter that decrements on the rising edge of the prescaler
input clock. The counter is enabled when at least one of the three timers is enabled (that is,
one or more of the timer enable bits are set) and is using the prescaler output as its source (that
is, one or more of the PCE bits are set).