STLED325 datasheet(50/62 Pages) STMICROELECTRONICS

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Commands

STLED325

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Doc ID 17576 Rev 1

Figure 18.

Interrupt bit mapping in Byte 2

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 hot-

key 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.

7.4

Address setting command

This command sets an address of the display memory or the address of the RTC register

map.

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.

Byte 2:

MSB

LSB

b7-b4 = Normal operation

b3-b0=Wake up operation

MSB

LSB

b4b3

b1b0

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