Motorola USB08 - Manual (Page 75)

Universal Serial Bus (USB) Interface
Data Communication via Endpoints EP1 and EP2
USB08 Evaluation Board Designer Reference Manual
MOTOROLA Universal Serial Bus (USB) Interface 75
To force the device not to send further STALL packets after the recovery
of the error, the host can use the standard device request
CLEAR_FEATURE. The responsible standard request handler
clearFeature():
• Hands over the code for the endpoint concerned (0
×
81 for EP1,
0
×
02 for EP2) to wIndex
• Writes ENDPOINT_HALT into wValue
• Forces the deletion of the STALL condition for the endpoint 1 or 2
A STALL condition of the EP0 resulting from an incorrect SETUP
request is reset automatically by the next arriving SETUP token.
4.7 Data Communication via Endpoints EP1 and EP2
The transmission of user data from or to the USB device takes place via
the endpoints 1 and 2. EP1 is an endpoint of the type IN and serves for
sending of information to the host. EP2 possesses the direction OUT
and is used by the device to receive data from the host.
All data traffic of the pay load endpoints EP1 and EP2, as well as the
administrative traffic of the endpoint EP0, leads to interrupt handling via
the interrupt service routine isrUSB(). The USB interrupt register 1
(UIR1) contains information about the exact source of the USB interrupt.
If the flag TXD1F is set, a transmit complete interrupt was indicated by
endpoint 1. If RXD2F is set, an endpoint 2 receive interrupt is pending.
Bit 7 6 5 4 3 2 1 Bit 0
Read: EOPF RSTF TXD2F RXD2F TXD1F RESUMF TXD0F RXD0F
Write:
Reset: 0 0 0 0 0 0 0 0
= Unimplemented
Figure 4-9. USB Interrupt Register 1 (UIR1)