Rainbow Electronics AT89C5131 - Manual (Page 119)

119
AT89C5131
4136A–USB–03/03
• Endpoint FIFO reset
Before using an endpoint, its FIFO will be reset. This action resets the FIFO pointer
to its original value, resets the byte counter of the endpoint (UBYCTLX and
UBYCTHX registers), and resets the data toggle bit (DTGL bit in UEPCONX).
The reset of an endpoint FIFO is performed by setting to 1 and resetting to 0 the
corresponding bit in the UEPRST register.
For example, in order to reset the Endpoint number 2 FIFO, write 0000 0100b then
0000 0000b in the UEPRST register.
Note that the endpoint reset doesn’t reset the bank number for ping-pong endpoints.
Read/Write Data FIFO
Read Data FIFO The read access for each OUT endpoint is performed using the UEPDATX register.
After a new valid packet has been received on an Endpoint, the data are stored into the
FIFO and the byte counter of the endpoint is updated (UBYCTLX and UBYCTHX regis-
ters). The firmware has to store the endpoint byte counter before any access to the
endpoint FIFO. The byte counter is not updated when reading the FIFO.
To read data from an endpoint, select the correct endpoint number in UEPNUM and
read the UEPDATX register. This action automatically decreases the corresponding
address vector, and the next data is then available in the UEPDATX register.
Write Data FIFO The write access for each IN endpoint is performed using the UEPDATX register.
To write a byte into an IN endpoint FIFO, select the correct endpoint number in UEP-
NUM and write into the UEPDATX register. The corresponding address vector is
automatically increased, and another write can be carried out.
Warning 1: The byte counter is not updated.
Warning 2: Do not write more bytes than supported by the corresponding endpoint.
FIFO Mapping
Figure 54. Endpoint FIFO Configuration
UEPNUM
Endpoint 0
Endpoint 6
UEPSTA0 UEPCON0 UEPDAT0
UEPSTA6 UEPCON6 UEPDAT6
0
1
2
3
4
5
6
SFR registers
UEPSTAX UEPCONX UEPDATX X
UBYCTH0 UBYCTL0
UBYCTH6 UBYCTL6
UBYCTHX UBYCTLX