em3027 EM Microelectronic, em3027 Datasheet - Page 16

• Manufacturer Part Number: em3027
• Description: Real-time Clock With I2c Or Spi Interface, Crystal Temperature Compensation, Battery Switchover And Trickle Charger
• Manufacturer: EM Microelectronic

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’s 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 a new value during reloading (Auto-Reload).
Timer values (TimLow, TimHigh), frequency selection (TD1, TD0) and mode selection (TROn) can be provided only when
the timer is stopped (TiOn = ‘0’).
NOTE: The “Timer Page” can also be used as a general purpose register when the timer function is not used.
8.5
The integrated thermometer has a resolution of 1°C.
The thermometer is disabled when (ThEn = ’0’) and enabled when (ThEn = ’1’). By default, the thermometer is enabled.
The thermometer is automatically disabled when VLOW1 status bit is at ‘1’.
When the thermometer is disabled (ThEn = ’0’), the Temp register can be written. The write operation computes
immediately a new compensation value for frequency correction.
Temp register uses also a cache memory to keep stable value during a whole transmission (read/write).
8.6
Compensation value (COMP_val) for temperature correction is computed each 1s or 16s (ThPer bit) when thermometer is
enabled (ThEn = ‘1’) or just once after Temp register is written and thermometer is disabled (ThEn = ’0’). After power-up the
compensation value is zero. The compensation value is computed according to the equation described in chapter 4.3.
Thermometer period is selectable by ThPer bit according to the table below:
When VLOW1 status bit is at ‘1’, the last computed compensation value is used. Temperature correction of crystal
frequency is provided continuously.
8.7
Before any EEPROM access (read/write), the bit EERefOn has to be cleared by the application to prevent from access
collision with the Configuration Registers. Then the application has to read EEBusy bit and if EEBusy = ‘0’ then EEPROM
access can be started.
After write command (“Transmission STOP”) the current state of EEPROM writing is monitored by EEBusy register bit at ‘1’.
EEBusy goes to ‘0’ when EEPROM writing is finished.
NOTE: (V
Copyright © 2008, EM Microelectronic-Marin SA
07/08 – rev B
Temperature sensor
Temperature compensation
EEPROM memory
CC
>V
R
prog
) V
CC
must be connected during whole EEPROM write.
TD1
Table 10 – Timer Frequency Selection
ThPer
0
0
1
1
0
1
Table 11 – Thermometer Period
TD0
0
1
0
1
Period in Seconds
Timer frequency
16 s
16
1 s
0.5 Hz
32 Hz
8 Hz
1 Hz
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EM3027