82801BA Datasheet, PDF (184/498 Pages) Intel Corporation – Intel 82801BA I/O Controller Hub 2 (ICH2) and Intel 82801BAM I/O Controller Hub 2 Mobile

Functional Description
Endpoint Field
An additional four-bit endpoint (ENDP) field, shown in Table 5-70, permits more flexible
addressing of functions in which more than one sub-channel is required. Endpoint numbers are
function specific. The endpoint field is defined for IN, SETUP, and OUT token PIDs only.
Table 5-70. Endpoint Field
Bit
0
1
2
3
Data Sent
ENDP 0
ENDP 1
ENDP 2
ENDP 3
5.16.4.5
Frame Number Field
The frame number field is an 11-bit field that is incremented by the host on a per frame basis. The
frame number field rolls over upon reaching its maximum value of x7FFh and is sent only for SOF
tokens at the start of each frame.
5.16.4.6
Data Field
The data field may range from 0 to 1023 bytes and must be an integral numbers of bytes. Data bits
within each byte are shifted out LSB first.
5.16.4.7
Cyclic Redundancy Check (CRC)
CRC is used to protect the all non-PID fields in token and data packets. In this context, these fields
are considered to be protected fields. The PID is not included in the CRC check of a packet
containing CRC. All CRCs are generated over their respective fields in the transmitter before bit
stuffing is performed. Similarly, CRCs are decoded in the receiver after stuffed bits have been
removed. Token and data packet CRCs provide 100% coverage for all single and double bit errors.
A failed CRC is considered to indicate that one or more of the protected fields is corrupted and
causes the receiver to ignore those fields, and, in most cases, the entire packet.
5-122
82801BA ICH2 and 82801BAM ICH2-M Datasheet