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PIC18F4550ESOSQTP Datasheet(PDF) 179 Page - Microchip Technology |
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PIC18F4550ESOSQTP Datasheet(HTML) 179 Page - Microchip Technology |
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179 / 430 page  © 2007 Microchip Technology Inc. Preliminary DS39632D-page 177 PIC18F2455/2550/4455/4550 17.5 USB Interrupts The USB module can generate multiple interrupt con- ditions. To accommodate all of these interrupt sources, the module is provided with its own interrupt logic structure, similar to that of the microcontroller. USB interrupts are enabled with one set of control registers and trapped with a separate set of flag registers. All sources are funneled into a single USB interrupt request, USBIF (PIR2<5>), in the microcontroller’s interrupt logic. Figure 17-8 shows the interrupt logic for the USB module. There are two layers of interrupt registers in the USB module. The top level consists of overall USB status interrupts; these are enabled and flagged in the UIE and UIR registers, respectively. The second level consists of USB error conditions, which are enabled and flagged in the UEIR and UEIE registers. An interrupt condition in any of these triggers a USB Error Interrupt Flag (UERRIF) in the top level. Interrupts may be used to trap routine events in a USB transaction. Figure 17-9 shows some common events within a USB frame and their corresponding interrupts. FIGURE 17-8: USB INTERRUPT LOGIC FUNNEL FIGURE 17-9: EXAMPLE OF A USB TRANSACTION AND INTERRUPT EVENTS BTSEF BTSEE BTOEF BTOEE DFN8EF DFN8EE CRC16EF CRC16EE CRC5EF CRC5EE PIDEF PIDEE SOFIF SOFIE TRNIF TRNIE IDLEIF IDLEIE STALLIF STALLIE ACTVIF ACTVIE URSTIF URSTIE UERRIF UERRIE USBIF Second Level USB Interrupts (USB Error Conditions) UEIR (Flag) and UEIE (Enable) Registers Top Level USB Interrupts (USB Status Interrupts) UIR (Flag) and UIE (Enable) Registers USB Reset SOF RESET SETUP DATA STATUS SOF SETUPToken Data ACK OUT Token Empty Data ACK START-OF-FRAME IN Token Data ACK SOFIF URSTIF 1 ms Frame Differential Data From Host From Host To Host From Host To Host From Host From Host From Host To Host Transaction Control Transfer(1) Transaction Complete Note 1: The control transfer shown here is only an example showing events that can occur for every transaction. Typical control transfers will spread across multiple frames. Set TRNIF Set TRNIF Set TRNIF |
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