EM3027

Copyright

 2013, EM Microelectronic-Marin SA

3027-DS.doc, Version 8.0, 25-Jan-13

16

www.emmicroelectronic.com

8.4

Timer function

The 16-bit count down timer can be enabled/disabled by TiOn bit.

The timer input frequency is selected by TD1, TD0 bits according to the following table:

TD1

TD0

Timer frequency

0

0

32 Hz

0

1

8 Hz

1

0

1 Hz

1

1

0.5 Hz

Table 10: Timer Frequency Selection

The timer can run in Zero-Stop or Auto-Reload mode (TROn bit

: ‘0’ = Zero-Stop mode, ‘1’ = Auto-Reload mode).

When TROn = ‘0’, then it is possible to read current value of the timer. If TROn = ‘1’, then last written value is read from

cache memory. The value in the cache memory is used as the new value for reloading (Auto-Reload mode).

Frequency selection (TD1, TD0) and mode selection (TROn) can be written

only when the timer is stopped (TiOn = ‘0’).

Timer values (TimLow, TimHigh) can be written only when the timer is stopped (

TiOn = ’0’ and TROn = ‘0’).

NOTE:

The “Timer Page” can also be used as a general purpose register when the timer function is not used.

8.5

Temperature measurement

The integrated thermometer has a resolution of 1°C.

The thermomet

er is disabled when ThEn = ’0’ and enabled when ThEn = ’1’. By default, the thermometer is enabled.

Thermometer period is selectable by ThPer bit according to the table below:

ThPer

Period in Seconds

0

1 s

1

16 s

Table 11: Thermometer Period

The thermometer is automatically disabled when VLOW1 stat

us bit is at ‘1’.

When the thermometer is disabled (ThEn = ’0’), the Temp register can be written. Temp register uses a cache memory to

keep stable value during a whole transaction (read/write).

8.6

Frequency compensation

There is a frequency compensation unit (FCU) inside EM3027. FCU compensates quartz crystal native frequency in

dependency on actual compensation value (COMP_val).

FCU is always running.

During chip power-up, i

f ThEn = ’1’ and VLOW1 = ‘0’ temperature measurement is enabled and COMP_val is computed.

Otherwise, COMP_val is set to 0 ppm.

In Normal mode, new compensation value is computed each 32 seconds. The onl

y exception is when ThEn = ‘1’ and

VLOW1 = ‘1’. In this case, temperature measurement and COMP_val computation are blocked and FCU uses the last

computed compensation value.

For the evaluation of COMP_val, actual content of Temp register (0x20) is used. The compensation value is computed

according to the equation described in paragraph 4.3.

Content of Temp register is updated either after a temperature measurement (when ThEn = '1' and VLOW1 = '0') or after

Temp register write transaction (when ThEn = '0'). After power-up content of Temp register is undefined.

If thermometer is disabled (ThEn = '0') user is advised to periodically update Temp register with actual ambient temperature

in order to have correct input data for COMP_val computation.