Service_USB 4 - Change transfer capacity
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## Name

Service_USB 4 - Change transfer capacity — Claim/release USB transfer capacity

## On Entry

R0 | 4 (reason code)
R1 | &80C00 (USB Service call)
R2 | Pointer to controller structure
R3 | device speed
R4 | transfer type
R5 | no of bytes to transfer
R6 | frame repeat (1 at isochronous, 0 at bulk and control,1-255 at interrupt)
R7 |
Value | Operation
0 | Test
1 | Claim
2 | Release

## On Exit

All registers preserved to pass on, else

R0 | 0 for success any other value indicates failure.
R1 | 0 to claim or preserved to pass on.
R2, R3, R4, R5, R6, R7 | preserved

## Use

Must be launched by a configuration application or the USB-Module itself at USB_PipeOpen/USB_PipeClose operation. Every USB host controller driver must support claiming of this Service call. If operation is successful (that means capacity is available, releases are always successful) a 0 must be filled into R0.

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