The Relationship Between the 8051 and USB Interrupts | Cypress Semiconductor
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The Relationship Between the 8051 and USB Interrupts
What is the difference between 8051 and USB interrupts in an FX2LP Device?
The 8051 interrupts and USB interrupts are handled differently. The USB interrupt vector generation is handled by the USB jump table (USBJmpTb.obj), and the 8051 interrupt vector generation is handled by the Keil compiler. The "#pragma noiv" statement in periph.c tells the Keil compiler to use the USB jump table for generating the interrupt vectors for the USB interrupts, instead of its own interrupt vector scheme, which follows the traditional 8051 scheme.