HS_USB 2.0 device
RM0082
482/844
Doc ID 018672 Rev 1
Figure 48.
In data memory
Table 392.
In data memory: buffer status quadlet bit assignments (for Non-
Isochronous IN)
Bit
Name
Description
[31:30]
BS
Buffer status.
This 2 bit field reports the status of the in buffer, according to encoding:
– 2’b00, Host ready. The descriptor is available to be processed by DMA.
– 2'b01, DMA busy. The DMA is still processing the descriptor.
– 2'b10, DMA done. Buffer data transfer completed by DMA.
– 2'b11, Host busy. The application is processing the descriptor.
[29:28]
Tx Sts
Transmit status.
This 2 bit field reports the status of the transmitted in data (according to
encoding), reflecting whether the in data has been correctly transmitted or
some errors occurred:
– 2'b00 = Success.
– 2'b01 = DESERR (descriptor transfer error).
– 2'b10 = Reserved.
– 2'b11 = BUFFER (data transfer error).
[27]
L
If set, it indicates that this descriptor is the last one of the chain.
[26:16]
Reserved
Read: undefined. Write: should be zero.
[15:00]
Tx Bytes
Number of bytes to be transmitted.
Its 16 bit width allows values ranging from 0 to 64 kbytes. for iso in
transactions, a maximum value of 16 kbytes is allowed by the 14 bit length
of the Tx bytes field.
Data Descriptor Pointer
IN Buffer Status Quadlet
Reserved
Buffer Pointer
Next Descriptor Pointer
Status Quadlet for
Non Iso-chronous IN
R
TxBytes
BS
Tx Sts
15:0
26:16
29:28
31:30
0
31
L
27
Status Quadlet for
Iso-chronous IN
Frame Number
TxBytes
BS
Tx Sts
13:0
26:16
29:28
31:30
L
27
PID
15:14