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10−4
10.2 Port Status Register
The port status page provides access to configuration and status information for each of the ports. The port is selected
by writing 0 to the Page_Select field and the desired port number to the Port_Select field in base register 7. Table 10−3
shows the configuration of the port status page registers and Table 10−4 shows the corresponding field descriptions.
If the selected port is not implemented, all registers in the port status page are read as 0.
Table 10−3. Page 0 (Port Status) Register Configuration
BIT POSITION
ADDRESS 0 1 2 3 4 5 6 7
1000 AStat BStat Ch Con Bias Dis
1001 Peer_Speed Int_enable Fault Reserved
1010 Reserved
1011 Reserved
1100 Reserved
1101 Reserved
1110 Reserved
1111 Reserved
Table 10−4. Page 0 (Port Status) Register Field Descriptions
FIELD SIZE TYPE DESCRIPTION
AStat 2 R TPA line state. This field indicates the TPA line state of the selected port, encoded as follows:
Code
Arb Value
11 Z
10 0
01 1
00 invalid
BStat 2 R TPB line state. This field indicates the TPB line state of the selected port. This field has the same encoding as
the AStat field.
Ch 1 R Child/parent status. A 1 indicates that the selected port is a child port. A 0 indicates that the selected port is
the parent port. A disconnected, disabled, or suspended port is reported as a child port. The Ch bit is invalid
after a bus reset until tree-ID has completed.
Con 1 R Debounced port connection status. This bit indicates that the selected port is connected. The connection
must be stable for the debounce time of approximately 341 ms for the Con bit to be set to 1. The Con bit is
cleared to 0 by system (hardware) reset and is unaffected by bus reset.
NOTE: The Con bit indicates that the port is physically connected to a peer PHY device, but the port is not
necessarily active.
Bias 1 R Debounced incoming cable bias status. A 1 indicates that the selected port is detecting incoming cable bias.
The incoming cable bias must be stable for the debounce time of 52 µs for the Bias bit to be set to 1.
Dis 1 RW Port disabled control. If the Dis bit is set to 1, the selected port is disabled. The Dis bit is cleared to 0 by
system (hardware) reset (all ports are enabled for normal operation following system (hardware) reset). The
Dis bit is not affected by bus reset.
Peer_Speed 3 R Port peer speed. This field indicates the highest speed capability of the peer PHY device connected to the
selected port, encoded as follows:
Code Peer Speed
000 S100
001 S200
010 S400
011−111 invalid
The Peer_Speed field is invalid after a bus reset until self-ID has completed.
NOTE: Peer speed codes higher than 010b (S400) are defined in IEEE Std 1394a-2000. However, the
PCI7x21/PCI7x11 controller is only capable of detecting peer speeds up to S400.