82801FB Datasheet, PDF (561/786 Pages) Intel Corporation – Intel I/O Controller Hub 6 (ICH6) Family

EHCI Controller Registers (D29:F7)
Bit
Description
LINK_ID_STS — RO. This field identifies the link interface.
15:12
0h = Hardwired. Indicates that it is a USB Debug Port.
11 Reserved. This bit returns 0 when read. Writes have no effect.
IN_USE_CNT — R/W. Set by software to indicate that the port is in use. Cleared by software to
10 indicate that the port is free and may be used by other software. This bit is cleared after reset. (This
bit has no affect on hardware.)
EXCEPTION_STS — RO. This field indicates the exception when the ERROR_GOOD#_STS bit is
set. This field should be ignored if the ERROR_GOOD#_STS bit is 0.
000 =No Error. (Default)
Note: this should not be seen, since this field should only be checked if there is an error.
9:7 _{001 =Transaction error: indicates the USB 2.0 transaction had an error (CRC, bad PID, timeout,}
etc.)
010 =Hardware error. Request was attempted (or in progress) when port was suspended or reset.
All Other combinations are reserved
ERROR_GOOD#_STS — RO.
6
0 = Hardware clears this bit to 0 after the proper completion of a read or write. (Default)
1 = Error has occurred. Details on the nature of the error are provided in the Exception field.
GO_CNT — WO.
0 = Hardware clears this bit when hardware sets the DONE_STS bit. (Default)
5
1 = Causes hardware to perform a read or write request.
NOTE: Writing a 1 to this bit when it is already set may result in undefined behavior.
WRITE_READ#_CNT — R/W. Software clears this bit to indicate that the current request is a read.
Software sets this bit to indicate that the current request is a write.
4
0 = Read (Default)
1 = Write
DATA_LEN_CNT — R/W. This field is used to indicate the size of the data to be transferred.
default = 0h.
For write operations, this field is set by software to indicate to the hardware how many bytes of data
in Data Buffer are to be transferred to the console. A value of 0h indicates that a zero-length packet
should be sent. A value of 1–8 indicates 1–8 bytes are to be transferred. Values 9–Fh are illegal
and how hardware behaves if used is undefined.
3:0
For read operations, this field is set by hardware to indicate to software how many bytes in Data
Buffer are valid in response to a read operation. A value of 0h indicates that a zero length packet
was returned and the state of Data Buffer is not defined. A value of 1–8 indicates 1–8 bytes were
received. Hardware is not allowed to return values 9–Fh.
The transferring of data always starts with byte 0 in the data area and moves toward byte 7 until the
transfer size is reached.
NOTES:
1. Software should do Read-Modify-Write operations to this register to preserve the contents of bits not being
modified. This include Reserved bits.
2. To preserve the usage of RESERVED bits in the future, software should always write the same value read
from the bit until it is defined. Reserved bits will always return 0 when read.
Intel^® I/O Controller Hub 6 (ICH6) Family Datasheet
561