RM0082
HS_USB 2.0 device
Doc ID 018672 Rev 1
483/844
Table 393.
In data memory:buffer status quadlet bit assignments (for Isochronous)
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]
Frame
Number (ISO)
11-bsit frame number in which the current iso-out packet is transmitted.
This 11 bit field gives the frame number in which the current iso-in packet
is transmitted, according to the following bits assignments:
[26:19] = Millisecond frame number.
[18:16] = Micro-frame number.
[15:14]
PID
Number of packets per microframe.
This 2 bit field indicates the number of packets per microframe for
isochronous (iso) in transfers during high-speed (hs) operation. The
application must program these bits in the descriptor (and they must be
the same for all descriptors of the same microframe) according to
encoding, such that the subsystem core returns an isochronous packet
with an appropriate data PID per frame:
– 2‘b00 = 1
– 2‘b01 = 1
– 2‘b10 = 2
– 2‘b11 = 3
Note: The PID field is for HS ISO transactions only. For FS ISO
transactions, this field is reserved.
[13:00]
Tx Bytes
(ISO)
Number of bytes to be transmitted.
The value of this field gives the number of bytes to be transmitted to USB
host. In case of non-iso in, its 16 bit length 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.