82801DB Datasheet, PDF (206/587 Pages) Intel Corporation – Intel 82801DB I/O Controller Hub 4 (ICH4)

Functional Description
Table 5-77 shows the debug port behavior related to the state of bits in the debug registers as well
as bits in the associated Port Status and Control register.
Table 5-77. Debug Port Behavior
OWNER_CNT ENABLED_CT
Port
Enable
0
X
X
1
0
X
1
1
0
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
Run /
Stop
X
X
0
1
0
0
1
1
Suspend
Debug Port Behavior
X
Debug port is not being used.
Normal operation.
X
Debug port is not being used.
Normal operation.
X
Debug port in Mode 1. SYNC
keepalives sent plus debug traffic
Debug port in Mode 2. SOF (and
only SOF) is sent as keepalive.
X
Debug traffic is also sent. Note that
no other normal traffic is sent out
this port, because the port is not
enabled.
Illegal. Host controller driver should
0
never put controller into this state
(enabled, not running and not
suspended).
1
Port is suspended. No debug traffic
sent.
Debug port in Mode 2. Debug
0
traffic is interspersed with normal
traffic.
1
Port is suspended. No debug traffic
sent.
5.17.10.1.1OUT Transactions
An Out transaction sends data to the debug device. It can occur only when the following are true:
• The debug port is enabled
• The debug software sets the GO_CNT bit
• The WRITE_READ#_CNT bit is set
The sequence of the transaction is:
1. Software sets the appropriate values in the following bits:
— USB_ADDRESS_CNF
— USB_ENDPOINT_CNF
— DATA_BUFFER[63:0]
— TOKEN_PID_CNT[7:0]
— SEND_PID_CNT[15:8]
— DATA_LEN_CNT
— WRITE_READ#_CNT (note: this will always be 1 for OUT transactions)
— GO_CNT (note: this will always be 1 to initiate the transaction)
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Intel^® 82801DB ICH4 Datasheet