ST62T08C datasheet(49/104 Pages) STMICROELECTRONICS

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ST6208C/ST6209C/ST6210C/ST6220C

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8-BIT TIMER (Cont’d)

8.2.4.2 Event Counter Mode

(TOUT = “0”, DOUT = “0”)

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 clearing the TOUT bit in

the TSCR register (i.e. as input) and clearing the

DOUT bit.

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. fTIMER Clock in Event Counter Mode

Figure 31. Event Counter Mode Operation

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

by the prescaler clock input (fINT/12). See Figure 32.

The user can select the prescaler division ratio us-

ing the PS[2:0] bits in the TSCR register. When TCR

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

bit transition is used to latch the DOUT bit in the

TSCR and, if the TOUT bit is set, DOUT is trans-

ferred to the TIMER pin. This operating mode allows

external signal generation on the TIMER pin. See

Figure 33.

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.

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).

Figure 32. Output Mode Control

Figure 33. Output Mode Operation

fPRESCALER

TIMER

XX1

COUNTER VALUE

TIMER PIN

VALUE 1

VALUE 2

XX2

TMZ

TIMER

TOUT

DOUT

LATCH

FFh

Counter

TIMER PIN

1st downcount:

Default output value is 0

At each zero event

DOUT has to be

copied to the TIMER

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