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EZ-USB FX2 Technical Reference Manual
Page 4-18 EZ-USB FX2 Technical Reference Manual v2.1
4.6 I²C-Compatible Bus Interrupt
Figure 4-6. I²C-Compatible Bus Interrupt-Enable Bits and Registers
Chapter 13, "Input/Output" describes the interface to the FX2’s I²C-Compatible Bus controller. The
FX2 uses two registers, I2CS (Control and Status) and I2DAT (Data), to transfer data over the bus.
An I²C-Compatible Bus Interrupt is asserted whenever one of the following occurs:
The DONE Bit (I2CS.0) makes a zero-to-one transition, signalling that the bus controller is
ready for another command.
The STOP bit (I2CS.6) makes a one-to-zero transition.
To enable the “Done” interrupt source, set EIE.1 to 1; to additionally enable the “Stop” interrupt
source, set STOPIE to 1. If both interrupts are enabled, the interrupt source may be determined by
checking the DONE and STOP Bits in the I2CS register.
To reset the Interrupt Request, write a zero to EXIF.5. Any firmware read or write to the I2DAT or
I2CS register also automatically clears the Interrupt Request.
While the I²C-Compatible Bus controller is generating the “stop” condition, it ignores accesses to
the I2CS and I2DAT registers. Firmware should therefore check the STOP Bit for zero before writ-
ing new data to I2CS or I2DAT.
EIE.1
EXIF.5(rd)
EXIF.5(0)
S
R
I
2
C-
Compatible
Bus
Interrupt
I
2
C-Compatible Bus
Interrupt Request
DONE
S
R
RD or WR
I2DAT register
I2CS
0xE678
I2DAT
0xE679
START STOP LASTRD ID1 ID0 BERR ACK
D7 D6 D5 D4 D3 D2 D1 D0
DONE
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