
EZ-USB FX2 Technical Reference Manual
Page 4-10 EZ-USB FX2 Technical Reference Manual v2.1
Figure 4-1. USB Interrupts
Referring to the logic inside the dotted lines, each USB interrupt source has an interrupt request
latch. IRQ bits are set automatically by the FX2; firmware clears an IRQ bit by writing a “1” to it.
The output of each latch is ANDed with an Interrupt Enable Bit and then ORed with all the other
USB Interrupt request sources.
The FX2 prioritizes the USB interrupts and constructs an Autovector, which appears in the
INT2VEC register. The interrupt vector values IV[4:0] are shown to the left of the interrupt sources
(shaded boxes); 0 is the highest priority, 31 is the lowest. If two USB interrupts occur simulta-
neously, the prioritization affects which one is first indicated in the INT2VEC register.
USB Interrupt
SUTOK
SUDAV
SOF
EIE.0
EXIF.4(rd)
EXIF.4(0)
S
R
FX2 "USB"
Interrupt
USBERRIE.7
USBERRIRQ.7 (1)
S
R
USBERRIRQ.7 (rd)
EP4ISOERR
EP6ISOERR
EP8ISOERR
0 IV4 IV3 IV2 IV1 IV0 0 0
INT2VEC
00
01
02
29
30
31
Interrupt Request Latch
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