Commands STLED325
Figure 18.
Interrupt bit mapping in Byte 2
Byte 2:
MSB
2ESERVED
24#
WATCHDOG
TIMER
24#
ALARM
24#
FAIL
/SCILLATOR
7AKEUP
PIN
,TO(
OR(TO,
7ATCHDOG
TIMER
24#ALARM
24#
FAIL
b3-b0=Wake up operation
LSB
/SCILLATOR
b7-b4 = Normal operation
!-6
In the normal mode of operation, when any FP or RC key is pressed or when alarm/watchdog is triggered, the STLED325 sets the flags in the above interrupt flag register and asserts the IRQ_N pin. The data which caused the interrupt to assert remains in the buffer until it is changed by another key-press. It is up to the micro processor to issue the read interrupt command to ascertain what caused the interrupt. If the micro processor does not issue the interrupt within a specific time, the old data is lost and only the latest data is reflected in the Interrupt Flag register.
In the standby mode of operation, only the hot-key will cause the interrupt flag to be set and the IRQ_N pin will be asserted. The micro processor should then read the interrupt to know what caused the wake-up operation before proceeding with the normal data communication or asserting STBY again if there is no action to be performed. Upon the first read of the hotkey data, the data in the buffer is cleared.
When the b4 of the above interrupt flag is set, then the µP should read the address 0x0F from the RTC register space to determine if the alarm was triggered. Only after determining this, the interrupt flag is cleared and the IRQ_N pin de-asserted.
The IRQ_N pin will only be de-asserted once the interrupt flags have been read. The chip will continue to send the interrupt periodically (approximately every 40us) to the main Host chip if the oscillator is down signifying to the Host chip that the frequency is out of spec.
This command sets an address of the display memory or the address of the RTC register map.
MSB
1 1 x b4 b3 b2 b1
LSB b0
The address range from 00h-0Fh represents the RTC register map. For writing data to RTC registers, initially the address command is sent followed by the RTC data.
10h-14h represents the 7-segment and discrete LED display correspondence. On power application, the address is set to 10h. In the auto-increment mode, when the address reached 0x14, the next ad-dress will be 0x10.
50/62 Doc ID 17576 Rev 1
