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10−3
Table 10−2. Base Register Field Descriptions (Continued)
FIELD SIZE TYPE DESCRIPTION
ISBR 1 R/W Initiate short arbitrated bus reset. This bit, if set to 1, instructs the PHY layer to initiate a short (1.3 µs)
arbitrated bus reset at the next opportunity. This bit is cleared to 0 by a bus reset.
NOTE: Legacy IEEE Std 1394-1995 compliant PHY layers can not be capable of performing short bus
resets. Therefore, initiation of a short bus reset in a network that contains such a legacy device results in a
long bus reset being performed.
Loop 1 R/W Loop detect. This bit is set to 1 when the arbitration controller times out during tree-ID start and may indicate
that the bus is configured in a loop. This bit is cleared to 0 by system (hardware) reset or by writing a 1 to this
register bit.
If the Loop and Watchdog bits are both set and the LLC is or becomes inactive, the PHY layer activates the
LLC to service the interrupt.
NOTE: If the network is configured in a loop, only those nodes which are part of the loop generate a
configuration-timeout interrupt. All other nodes instead time out waiting for the tree-ID and/or self-ID process
to complete and then generate a state time-out interrupt and bus-reset.
Pwr_fail 1 R/W Cable power failure detect. This bit is set to 1 whenever the CPS input transitions from high to low indicating
that cable power may be too low for reliable operation. This bit is cleared to 0 by system (hardware) reset or
by writing a 1 to this register bit.
Timeout 1 R/W State time-out interrupt. This bit indicates that a state time-out has occurred (which also causes a bus reset
to occur). This bit is cleared to 0 by system (hardware) reset or by writing a 1 to this register bit.
Port_event 1 R/W Port event detect. This bit is set to 1 upon a change in the bias (unless disabled) connected, disabled, or fault
bits for any port for which the port interrupt enable (Int_enable) bit is set. Additionally, if the Watchdog bit is
set, the Port_event bit is set to 1 at the start of resume operations on any port. This bit is cleared to 0 by
system (hardware) reset or by writing a 1 to this register bit.
Enab_accel 1 R/W Enable accelerated arbitration. This bit enables the PHY layer to perform the various arbitration acceleration
enhancements defined in IEEE Std 1394a-2000 (ACK-accelerated arbitration, asynchronous fly-by
concatenation, and isochronous fly-by concatenation). This bit is cleared to 0 by system (hardware) reset
and is unaffected by bus reset.
Enab_multi 1 R/W Enable multispeed concatenated packets. This bit enables the PHY layer to transmit concatenated packets
of differing speeds in accordance with the protocols defined in IEEE Std 1394a-2000. This bit is cleared to 0
by system (hardware) reset and is unaffected by bus reset.
Page_Select 3 R/W Page_Select. This field selects the register page to use when accessing register addresses 8 through 15.
This field is cleared to 0 by a system (hardware) reset and is unaffected by bus reset.
Port_Select 4 R/W Port_Select. This field selects the port when accessing per-port status or control (for example, when one of
the port status/control registers is accessed in page 0). Ports are numbered starting at 0. This field is cleared
to 0 by system (hardware) reset and is unaffected by bus reset.