at89c5131 ATMEL Corporation, at89c5131 Datasheet - Page 122

• Manufacturer Part Number: at89c5131
• Description: 8-bit Flash Microcontroller With Full Speed Usb Device At89c5131
• Manufacturer: ATMEL Corporation

Read/Write Data FIFO
Read Data FIFO
Write Data FIFO
FIFO Mapping
Figure 58. Endpoint FIFO Configuration
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Endpoint 0
Endpoint 6
AT89C5131
UEPSTA0
UEPSTA6
UBYCTH0
UBYCTH6
•
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.
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.
UEPCON0
UEPCON6
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.
UBYCTL0
UBYCTL6
UEPDAT0
UEPDAT6
UEPNUM
0
1
2
3
4
5
6
X
UEPSTAX
UBYCTHX
SFR registers
UEPCONX
UBYCTLX
UEPDATX
4136C–USB–04/05