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To start a "one-shot" timer again after it has elapsed, the user simply needs to write
a start command to the timer control register again. If you want to retrigger a "one-
shot" timer that has not yet elapsed, you must first stop the timer and then start it
again. This also applies when it is used as a "cyclic" timer. The user must first stop
the counter by writing "11" to the relevant bits of the control register before the
timer can start or continue counting with a start command (by writing "01" or "10" to
the relevant bits).
A resume counting command to a previously stopped counter starts the counter
from the start value again if the counter had reached 0 when it stopped.
To ensure that the higher byte always matches the lower byte when reading out the
timer values via the 8-bit data bus, the user must always read the lower byte first
and then the higher byte (while the lower byte is being read, the higher byte is
copied to register and it is then read from this register). Word access to this register
is therefore not permitted.
Note
Between all operations with timers (for example, stopping and restarting), always
wait one clock period of the timer clock pulse rate.
Timer-Type Register (address 0x31D; write only):
Bit 0
Bit 1
Bit 2
Bit 3
PROFIBUS Controller SPC 4®-2 LF
C79000-G8976-C157-3
0
Timer0 is a cyclic timer (status following reset).
1
Timer0 is a "one-shot" timer
0
Timer1 is a cyclic timer (status following reset).
1
Timer1 is a "one-shot" timer
0
Timer2 is a cyclic timer (status following reset).
1
Timer2 is a "one-shot" timer
0
Timer3 is a cyclic timer (status following reset).
1
Timer3 is a "one-shot" timer
ASIC Interface
105
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