ST72260G1B6/XXX View Datasheet(PDF) - STMicroelectronics

Part Name

Description

Manufacturer

ST72260G1B6/XXX

8-BIT MCU WITH FLASH OR ROM MEMORY, ADC, TWO 16-BIT TIMERS, I2C, SPI, SCI INTERFACES

STMicroelectronics 

ST72260G, ST72262G, ST72264G

WATCHDOG TIMER (Cont’d)

Figure 34. Exact Timeout Duration (tmin and tmax)

WHERE:

tmin0 = (LSB + 128) x 64 x tOSC2

tmax0 = 16384 x tOSC2

tOSC2 = 125ns if fOSC2=8 MHz

CNT = Value of T[5:0] bits in the WDGCR register (6 bits)

MSB and LSB are values from the table below depending on the timebase selected by the TB[1:0] bits

in the MCCSR register

TB1 Bit

TB0 Bit

(MCCSR Reg.) (MCCSR Reg.)

0

0

0

1

1

0

1

1

Selected MCCSR

Timebase

2ms

4ms

10ms

25ms

MSB

4

8

20

49

LSB

59

53

35

54

To calculate the minimum Watchdog Timeout (tmin):

IF CNT <

M------S----B---

4

THEN tmin = tm in0 + 16384 × CNT × tosc2

ELSE tmin = tm in0 +

16384

×





C

N

T

–

4----C-----N-----T--

MSB





+

(192 +

LSB)

× 64 ×

4----C-----N-----T--

MSB

× tosc2

To calculate the maximum Watchdog Timeout (tmax):

IF CNT ≤

M------S----B---

4

THEN tmax = tm ax0 + 16384 × CNT × tosc2

ELSE tmax = tm ax0 +

16384 × C NT –

4----C-----N-----T--

MSB





+

(192 +

LSB)

× 64 ×

4----C-----N-----T--

MSB

× tosc2

Note: In the above formulae, division results must be rounded down to the next integer value.

Example:

With 2ms timeout selected in MCCSR register

Value of T[5:0] Bits in

WDGCR Register (Hex.)

00

3F

Min. Watchdog

Timeout (ms)

tmin

1.496

128

Max. Watchdog

Timeout (ms)

tmax

2.048

128.552

50/171

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