AN2827

STATUS register and ATN pin

Doc ID 15047 Rev 1

19/30

6

STATUS register and ATN pin

Refer to the STCF05 datasheet for a detailed description of each bit.

When the status register is latched, reading and writing to the registers is still possible, but

the bits TRIG_EN and TCH_ON in the COMMAND register and AUXL register cannot be

changed until the device is unlatched. It is necessary to read the STATUS register to unlatch

the device.

The ATN pin is also pulled down when the internal timer reaches zero in flash mode. In this

case, the ATN pin is pulled down for 11 µs only. It is recommended to connect the ATN pin to

the interrupt input of the microcontroller. If it is not connected to the interrupt input, the ATN

pin should be polled fast enough not to miss the 11 µs pulse; for example, by a programming

loop which is entered after the start of flash mode. This loop will run until the ATN pin goes

Low. It is recommended to make a timeout of such a loop.

Table 9.

STATUS register bits

Bit name

LED_S

F_RUN

LED_F

NTC_W

NTC_H

OT_F

OC_F

VOUTOK_N

MSB

LSB

Table 10.

Effect of the STATUS register bits on the operation of the device

Bit Name

LED_S

F_RUN

STAT_REG

LED_O

STAT_REG

NTC_W

STAT_REG

NTC_H

STAT_REG

OT_F

STAT_REG

OC_F

STAT_REG

VOUTOK_N

STAT_REG

Default

value

0

00000

0

0

YES

NO

YES

YES

YES

YES

No

YES

Forces

READY

mode

when set

NO

NO

YES

NO

YES

YES

NO

YES

Sets ATN

LOW when

set

YES

NO

YES

YES

YES

YES

NO

YES

1.

YES means that the bit is set by internal signals and is reset to its default value by an I²C read operation of STAT_REG.

NO means that the bit is set and reset by internal signals in real-time.