ST6208C/ST6209C/ST6210C/ST6220C
8-BIT TIMER (Cont’d)
8.2.4.2 Event Counter Mode
(TOUT = “0”, DOUT = “0”)
bit transition is used to latch the DOUT bit in the
TSCR and, if the TOUT bit is set, DOUT is trans-
ferredto the TIMERpin. Thisoperatingmodeallows
external signal generation on the TIMER pin. See
Figure 33.
In this mode, the TIMER pin is the input clock of
the Timer prescaler which is decremented on eve-
ry rising edge of the input clock (allowing event
count). See Figure 30 and Figure 31.
This mode is selected by setting the TOUT bit in
the TSCR register (i.e. as output) and setting the
DOUT bit to output a high level or clearing the
DOUT bit to output a low level.
This mode is selected by clearing the TOUT bit in
the TSCR register (i.e. as input) and clearing the
DOUT bit.
Note: As soon as the TOUT bit is set, The timer
pin is configured as output push-pull regardless of
the corresponding I/O port control registers setting
(if the TIMER pin is multiplexed).
Note: In this mode, if the TIMER pin is multi-
plexed, the corresponding port control bits have to
be set in input with pull-up configuration.
Figure 30. f
Clock in Event Counter Mode
TIMER
Figure 32. Output Mode Control
f
TIMER
PRESCALER
TIMER
LATCH
Figure 31. Event Counter Mode Operation
TMZ
TOUT DOUT
COUNTER VALUE
VALUE 1
XX1
Figure 33. Output Mode Operation
Counter
FFh
VALUE 2
XX2
TIMER PIN
At each zero event
TIMER PIN
1
DOUT has to be
copied to the TIMER
pin
8.2.4.3 Output Mode
(TOUT = “1”, DOUT = “data out”)
In Output mode, the TIMER pin is connected to the
DOUT latch, hence the Timer prescaler is clocked
bytheprescalerclockinput(f /12).SeeFigure32.
INT
The user can select the prescaler division ratio us-
ingthePS[2:0]bitsintheTSCR register. WhenTCR
decrements to zero, it sets the TMZ bit in the TSCR.
The TMZ bit can be tested under program control to
perform a timer function whenever it goes high and
has to be cleared by the user. The low-to-high TMZ
st
1
downcount:
Default output value is 0
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1
STMICROELECTRONICS [ ST ]
