TAS1020 Datasheet, PDF (57/93 Pages) Texas Instruments – USB Streaming Controller

A.4.3.3 USB Out End-Point – X Buffer Data Count Byte (OEPDCNTXx)
The USB out end-point X buffer data count byte contains the 7-bit value used to specify the amount of data received
in a data packet from the host PC. The no acknowledge status bit is also contained in this byte.
Bit
Mnemonic
Type
7
NACK
R/W
6
DCNTX6
R/W
5
DCNTX5
R/W
4
DCNTX4
R/W
3
DCNTX3
R/W
2
DCNTX2
R/W
1
DCNTX1
R/W
0
DCNTX0
R/W
BIT MNEMONIC
NAME
7 NACK
No acknowledge
6:0 DCNTX(6:0) X Buffer data count
DESCRIPTION
The no acknowledge status bit is set to a 1 by the UBM at the end of a successful USB out
transaction to this end-point to indicate that the USB end-point X buffer contains a valid data
packet and that the X buffer data count value is valid. For control, interrupt, or bulk end-points,
when this bit is set to a 1, all subsequent transactions to the end-point will result in a NACK
handshake response to the host PC. Also for control, interrupt, and bulk end-points to enable
this end-point to receive another data packet from the host PC, this bit must be cleared to a 0
by the MCU. For isochronous end-points, a NACK handshake response to the host PC is not
allowed. Therefore, the UBM ignores this bit in reference to receiving the next data packet.
However, the MCU or DMA must clear this bit before reading the data packet from the buffer.
The X buffer data count value is set by the UBM when a new data packet is written to the X
buffer for the out end-point. The 7-bit value is set to the number of bytes in the data packet for
control, interrupt, or bulk end-point transfers and is set to the number of samples in the data
packet for isochronous end-point transfers. To determine the number of samples in the data
packet for isochronous transfers, the bytes per sample value in the configuration byte is
used. The data count value is read by the MCU or DMA to obtain the data packet size.
A.4.3.4 USB Out End-Point – X and Y Buffer Size Byte (OEPBSIZx)
The USB out end-point X and Y buffer size byte contains the 8-bit value used to specify the size of the two data buffers
to be used for this end-point.
Bit
Mnemonic
Type
7
BSIZ7
R/W
6
BSIZ6
R/W
5
BSIZ5
R/W
4
BSIZ4
R/W
3
BSIZ3
R/W
2
BSIZ2
R/W
1
BSIZ1
R/W
0
BSIZ0
R/W
BIT MNEMONIC
NAME
7:0 BSIZ(7:0)
Buffer size
DESCRIPTION
The X and Y buffer size value is set by the MCU to program the size of the X and Y data packet
buffers. Both buffers are programmed to the same size based on this value. This value is in
8-byte units. For example, a value of 18h results in the size of the X and Y buffers each being
set to 192 bytes.
A.4.3.5 USB Out End-Point – X Buffer Base Address Byte (OEPBBAXx)
The USB out end-point X buffer base address byte contains the 8-bit value used to specify the base memory location
for the X data buffer for a particular USB out end-point.
Bit
Mnemonic
Type
7
BBAX10
R/W
6
BBAX9
R/W
5
BBAX8
R/W
4
BBAX7
R/W
3
BBAX6
R/W
2
BBAX5
R/W
1
BBAX4
R/W
0
BBAX3
R/W
BIT MNEMONIC
NAME
DESCRIPTION
7:0 BBAX(10:3)
X Buffer base address
The X buffer base address value is set by the MCU to program the base address location in
memory to be used for the X data buffer. A total of 11 bits is used to specify the base address
location. This byte specifies the most significant 8 bits of the address. All 0s are used by the
hardware for the three least significant bits.
A.4.3.6 USB Out End-Point – Configuration Byte (OEPCNFx)
The USB out end-point configuration byte contains the various bits used to configure and control the end-point. Note
that the bits in this byte take on different functionality based on the type of end-point defined. The control, interrupt,
and bulk end-points function differently than the isochronous end-points.
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