RM0402 Rev 6 987/1163
RM0402 USB on-the-go full-speed (OTG_FS)
1122
Peripheral Tx FIFOs
The core has a dedicated FIFO for each IN endpoint. The application configures FIFO sizes
by writing the endpoint 0 transmit FIFO size register (OTG_DIEPTXF0) for IN endpoint0 and
the device IN endpoint transmit FIFOx registers (OTG_DIEPTXFx) for IN endpoint-x.
29.11.2 Host FIFO architecture
Figure 341. Host-mode FIFO address mapping and AHB FIFO access mapping
Host Rx FIFO
The host uses one receiver FIFO for all periodic and nonperiodic transactions. The FIFO is
used as a receive buffer to hold the received data (payload of the received packet) from the
USB until it is transferred to the system memory. Packets received from any remote IN
endpoint are stacked back-to-back until free space is available. The status of each received
packet with the host channel destination, byte count, data PID and validity of the received
data are also stored into the FIFO. The size of the receive FIFO is configured in the receive
FIFO size register (OTG_GRXFSIZ).
The single receive FIFO architecture makes it highly efficient for the USB host to fill in the
receive data buffer:
• All IN configured host channels share the same RAM buffer (shared FIFO)
• The OTG_FS core can fill in the receive FIFO up to the limit for any sequence of IN
tokens driven by the host software
The application receives the Rx FIFO not-empty interrupt as long as there is at least one
packet available for download. It reads the packet information from the receive status read
and pop register and finally pops the data off the receive FIFO.
MSv36930V1
OTG_HNPTXFSIZ[31:16]
Rx FIFO control
Any channel DFIFO pop
access from AHB
Rx packets
OTG_GRXFSIZ[15:0]
MAC push
Rx start address fixed to 0
A1=0
Single data
FIFO
OTG_HNPTXFSIZ[15:0]
Non-periodic Tx
FIFO control
Any non-periodic
channel DFIFO push
access from AHB
Non-periodic
Tx packets
MAC pop
OTG_HPTXFSIZ[31:16]
OTG_HPTXFSIZ[15:0]
Periodic Tx FIFO
control (optional)
Any periodic channel
DFIFO push access
from AHB
Periodic Tx
packets
MAC pop
To Next Page
Loading...
Need help?
General
