HFC-SUSB Cologne Chip AG, HFC-SUSB Datasheet - Page 30

• Manufacturer Part Number: HFC-SUSB
• Description: Isdn S/t HDLC Basic Rate Controller
• Manufacturer: Cologne Chip AG

863 C EC2
3.4.2 FIFO control bytes
3.4.2.1 FIFO control bytes for receive FIFOs
For the receive FIFOs (IN transfer on enpoints 1..4 or 5..8) the first two data bytes of the first data packet
are used as FIFO control bytes (see also Table 3 and Figure 4). Then the data bytes of the FIFO selected
by the endpoint number are transmitted.
Bit
Name
Bit Name
F_FILL[7:0]
STATES[3:0]
ERR
EoF
Table 3: FIFO control bytes for receive FIFOs
The HFC-S USB assumes a data transfer as finished if the data packet size is less than wMaxPacketSize
(see also USB_SIZE register).
For receive FIFOs the EoF-bit is set to '1' if the HDLC frame ends after the data transfer. If the last data
packet has the same length as wMaxPacketSize an empty data packet is sent next (see Figure 4).
As you can see in the figure below the FIFO control bytes are only sent in the first data packet of a
transfer.
Figure 4: FIFO control bytes for receive FIFOs
# _V ("
*
The wMaxPacketSize in the USB endpoint descriptors must be the same as the size selected in the
USB_SIZE register (or USB_SIZE_I register for isochronous transfers).
important!
7
STATES[3:0]
6
FIFO Control Bytes for Receive FIFOs (Host Receives Data)
5
Description
Bits 7..0 of the F_FILL register (indicate which FIFOs are over threshold)
Bits 3..0 of STATES register (current state of TE/NT state machine)
'1'
'1'
In transparent mode this bit is always '0'.
4
Byte 1
A receive data error on an isochronous OUT transfer has occured. This bit
is automatically reset after the next ISO-OUT transfer whithout errors.
end of HDLC frame after data transfer
3
unused
2
ERR EoF
1
0
7
6
5
F_FILL[7:0]
4
Byte 2
3
2
Cologne
Chip
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1
0