Freescale-semiconductor DSP56366 User Manual download pdf (Page 244)

Timer Modes of Operation

DSP56366 24-Bit Digital Signal Processor User Manual, Rev. 4

11-14 Freescale Semiconductor

11.4.1.2 Timer Pulse (Mode 1)

In this mode, the timer generates a compare interrupt when the timer count reaches a preset value. In

addition, timer 0 provides an external pulse on its TIO0 signal.

Set the TE bit to clear the counter and enable the timer. The value to which the timer is to count is loaded

into the TCPR. The counter is loaded with the TLR value when the first timer clock signal is received. The

TIO0 signal is loaded with the value of the INV bit. The timer clock signal can be taken from either the

DSP56366 clock divided by two (CLK/2) or from the prescaler clock output. Each subsequent clock signal

increments the counter.

When the counter matches the TCPR value, the TCF bit in TCSR is set and a compare interrupt is

generated if the TCIE bit is set. The polarity of the TIO0 signal is inverted for one timer clock period.

If the TRM bit is set, the counter is loaded with the TLR value on the next timer clock and the count is

resumed. If the TRM bit is cleared, the counter continues to be incremented on each timer clock.

This process is repeated until the TE bit is cleared (disabling the timer).

The value of the TLR sets the delay between starting the timer and the generation of the output pulse. To

generate successive output pulses with a delay of X clocks between signals, the TLR value should be set

to X/2 and the TRM bit should be set.

This process is repeated until the timer is disabled (i.e., TE is cleared).

If the counter overflows, the TOF bit is set, and if TOIE is set, an overflow interrupt is generated.

The counter contents can be read at any time by reading the TCR.

11.4.1.3 Timer Toggle (Mode 2)

In this mode, the timer generates a periodic interrupt; timer 0 also toggles the polarity of the TIO0 signal.

Set the TE bit in the TCR to clear the counter and enable the timer. The value the timer is to count is loaded

into the TPCR. The counter is loaded with the TLR value when the first timer clock signal is received. The

TIO0 signal is loaded with the value of the INV bit. The timer clock signal can be taken from either the

DSP56366 clock divided by two (CLK/2) or from the prescaler clock output. Each subsequent clock signal

increments the counter.

Bit Settings Mode Characteristics

TC3 TC2 TC1 TC0 TIO0 Clock # KIND NAME

0001OutputInternal1 Timer Pulse

Bit Settings Mode Characteristics

TC3 TC2 TC1 TC0 TIO0 Clock # KIND NAME

0010OutputInternal0 Timer Toggle

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Freescale-semiconductor DSP56366 User Manual Page 244