Designer Reference Manual
USB08 Evaluation Board
70
Universal Serial Bus (USB) Interface
MOTOROLA
Universal Serial Bus (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
.
// Structure of Setup Packet sent during
// SETUP Stage of Standard Device Requests
// according to USB1.1 spec page 183
//
typedef struct {
uchar bmRequestType; // Characteristics (Dir,Type,Recipient)
uchar bRequest; // Standard Request Code
iword wValue; // Value Field
iword wIndex; // Index or Offset Field
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 7
6
5
4
3
2
1
Bit 0
Read:
R0SEQ
SETUP
0
0
RP0SIZ3
RP0SIZ2
RP0SIZ1
RP0SIZ0
Write:
Reset:
Unaffected by reset
= Unimplemented
Figure 4-6. USB Status Register 0 (USR0)
Содержание MC68HC908JB8
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