Designer Reference Manual USB08 Evaluation Board
70 Universal Serial Bus (USB) Interface MOTOROLA
Universal Serial Bu s (USB) Interface
refers to a SETUP or an OUT packet. Therefore, the flag SETUP in the
USB status register 0 (USR0) has to be examined. If this flag is set, the
last token received by EP0 was a SETUP token and the interrupt routine
is branched to the function for handling of SETUP transactions,
handleSETUP().
In the USB status register 0 (USR0) the function handleSETUP() finds
not only the type of the transaction (SETUP or OUT), but can also
determine the number of received bytes. In the case of a SETUP
transaction, the data length is always defined as eight bytes. Therefore,
USR0 should contain the value 0×48.
The eight bytes received by endpoint 0 are available in the eight
registers UE0D0–UE0D7 and will be transferred into the buffer variable
SetupBuffer. This variable of the type setup_buffer is explained in the
following excerpt from U08USB.H.
// Structure of Setup P acket sent during
// SETUP Stage of Standard Device Requests
// according to USB1.1 spec page 183
//
typedef struct {
uchar bmRequestType; // Characteri st ics (Dir,Type,Recipient)
uchar bRequest; // Standard Request Co de
iword wValue; // Value Field
iword wIndex; // Index or Offset Fie ld
iword wLength; // No. of Bytes to transfer (Data Stage)
} setup_buffer;
The field bmRequestType must contain the value 0 in bits 5 and 6;
otherwise, it is not a standard device request.
Bit 7654321Bit 0
Read: R0SEQ SETUP 0 0 RP0SIZ3 RP0SIZ2 RP0SIZ1 RP0SIZ0
Write:
Reset: Unaffected by reset
= Unimplemented
Figure 4-6. USB Status Register 0 (USR0)