RM0352 datasheet(60/138 Pages) STMICROELECTRONICS

60 / 138 page

ARM© dual timer module (SP804)

RM0352

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DocID024647 Rev 1

Load register, TimerXLoad

The TimerXLoad register is a 32-bit register that contains the value from which the counter

is to decrement. This is the value used to reload the counter when Periodic mode is

enabled, and the current count reaches zero.

When this register is written to directly, the current count immediately resets to the new

value at the next rising edge of TIMCLK which is enabled by TIMCLKENX.

Note:

The minimum valid value for TimerXLoad is 1. If TimerXload is set to 0 then an interrupt is

generated immediately.

The value in this register is also overwritten if the TimerXBGLoad register is written to, but

the current count is not immediately affected.

If values are written to both the TimerXLoad and TimerXBGLoad registers before an

enabled rising edge on TIMCLK, then on the next enabled TIMCLK edge the value written to

the TimerXLoad value replaces the current count value. After that, each time the counter

reaches zero the current count value resets to the value written to TimerXBGLoad.

Reading from the TimerXLoad register at any time after the two writes have occurred

retrieves the value written to TimerXBGLoad. That is, the value read from TimerXLoad is

always the value that takes effect for Periodic mode after the next time the counter reaches

zero.

Current value register, TimerXValue

The TimerXValue register is a 32-bit read-only register that gives the current value of the

decrementing counter.

After a load operation has taken place by writing a new load value to TimerXLoad, the

TimerXValue register reflects the new load value immediately in the PCLK clock domain

without waiting for the next TIMCLK edge qualified by TIMCLKENX.

Note:

The most significant 16 bits of the 32-bit TimerXValue register are not automatically set to 0

when in 16-bit timer mode. If the timer is in 16-bit mode then the most significant 16 bits of

the TimerXValue register might have a non-zero value if the timer was previously in 32-bit

mode and a write to the TimerXLoad register has not occurred since the change to 16-bit

mode.

RM0352 датащи(PDF) 60 Page - STMicroelectronics