AS3911B Datasheet, PDF (46/155 Pages) ams AG – NFC Initiator / HF Reader IC

Figure 33:
SPI Read Timing
/S S
SCLK
MOSI
M ISO
AS3911B – 46
Application Information
DATAI
tD O D
DATAO
...
...
...
... _{D A TA O}
tD O H Z
Interrupt Interface
There are three interrupt registers implemented in the AS3911B
(Main Interrupt Register and auxiliary Timer and NFC Interrupt
Register and Error and Wake-up Interrupt Register). Main
Interrupt Register contains information about six interrupt
sources, while two bits reference to interrupt sources detailed
in Timer and NFC Interrupt Register and Error and Wake-up
Interrupt Register.
When an interrupt condition is met the source of interrupt bit
is set in the Main Interrupt Register and the IRQ pin transitions
to high.
The microcontroller then reads the Main Interrupt Register to
distinguish between different interrupt sources. The interrupt
registers 0x17, 0x18 and 0x19 are to be read in one attempt.
After a particular Interrupt Register is read, its content is reset
to 0. Exceptions to this rule are the bits pointing to auxiliary
registers. These bits are only cleared when corresponding
auxiliary register is read. IRQ pin transitions to low after the
interrupt bit(s) which caused its transition to high has been
read. Please note that there may be more than one interrupt
bits set in case the microcontroller did not immediately read
the interrupt registers after the IRQ signal was set and another
event causing interrupt occurred. In that case the IRQ pin
transitions to low after the last bit which caused interrupt is
read.
In case an interrupt from a certain source is not required it can
be disabled by setting corresponding bit in the Mask Interrupt
registers. In case of masking a certain interrupt source the
interrupt is not produced, but the source of interrupt bit is still
set in interrupt registers.
ams Datasheet: 2014-Jun-12 [v1-08]