DSP56303 datasheet(215/292 Pages) FREESCALE

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Triple Timer Module Programming Model

DSP56303 User’s Manual, Rev. 2

Freescale Semiconductor

9-23

9.4.3 Timer Prescaler Count Register (TPCR)

The TPCR is a read-only register that reflects the current value in the prescaler counter.

Table 9-1. Timer Prescaler Load Register (TPLR) Bit Definitions

Bit Number

Bit Name

Reset Value

Description

Reserved. Write to zero for future compatibility.

22–21

PS[1–0]

Prescaler Source

Control the source of the prescaler clock. The prescaler’s use of a TIO signal

is not affected by the TCSR settings of the timer of the corresponding TIO

signal. If the prescaler source clock is external, the prescaler counter is

incremented by signal transitions on the TIO signal. The external clock is

internally synchronized to the internal clock. The external clock frequency

must be lower than the DSP56303 internal operating frequency divided by 4

(that is, CLK/4).

Note:

To ensure proper operation, change the PS[1–0] bits only when the

prescaler counter is disabled. Disable the prescaler counter by

clearing TCSR[TE] of each of three timers.

PS1

PS0

Prescaler Clock Source

Internal CLK/2

TIO0

TIO1

TIO2

20–0

PL[20–0]

Prescaler Preload Value

Contains the prescaler preload value, which is loaded into the prescaler

counter when the counter value reaches 0 or the counter switches state from

disabled to enabled. If PL[20–0] = N, then the prescaler counts N+1 source

clock cycles before generating a prescaler clock pulse. Therefore, the

prescaler divide factor = (preload value) + 1.

PC20

PC19

PC18

PC17

PC16

PC15

PC14

PC13

PC12

9876

5432

PC11

PC10

PC9

PC8

PC7

PC6

PC5

PC4

PC3

PC2

PC1

PC0

Reserved bit; read as 0; write to 0 for future compatibility

Figure 9-22. Timer Prescaler Count Register (TPCR)

Table 9-2. Timer Prescaler Count Register (TPCR) Bit Definitions

Bit Number

Bit Name

Reset Value

Description

23–21

Reserved. Write to zero for future compatibility.

20–0

PC[20–0]

Prescaler Counter Value

Contain the current value of the prescaler counter.

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