Datasheet


    
SLLS418I − JUNE 2000 − REVISED DECEMBER 2004
36
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
POST OFFICE BOX 1443
• HOUSTON, TEXAS 77251−1443
PRINCIPLES OF OPERATION
status transfer
A status transfer is initiated by the PHY when there is status information to be transferred to the LLC. The PHY
waits until the interface is idle before starting the transfer. The transfer is initiated by the PHY asserting status
(01b) on the CTL terminals, along with the first two bits of status information on the D[0:1] terminals. The PHY
maintains CTL = Status for the duration of the status transfer. The PHY may prematurely end a status transfer
by asserting something other than status on the CTL terminals. This occurs if a packet is received before the
status transfer completes. The PHY continues to attempt to complete the transfer until all status information has
been successfully transmitted. There is at least one idle cycle between consecutive status transfers.
The PHY normally sends just the first four bits of status to the LLC. These bits are status flags that are needed
by the LLC state machines. The PHY sends an entire 16-bit status packet to the LLC after a read register
request, or when the PHY has pertinent information to send to the LLC or transaction layers. The only defined
condition where the PHY automatically sends a register to the LLC is after self-ID, where the PHY sends the
physical-ID register that contains the new node address. All status transfers are either 4 or 16 bits unless
interrupted by a received packet. The status flags are considered to have been successfully transmitted to the
LLC immediately upon being sent, even if a received packet subsequently interrupts the status transfer. Register
contents are considered to have been successfully transmitted only when all 8 bits of the register have been
sent. A status transfer is retried after being interrupted only if any status flags remain to be sent or if a register
transfer has not yet completed.
The definition of the bits in the status transfer is shown in Table 19 and the timing is shown in Figure 17.
Table 19. Status Bits
BIT(s) NAME DESCRIPTION
0 Arbitration reset gap Indicates that the PHY has detected that the bus has been idle for an arbitration reset gap time (as defined in
the IEEE 1394-1995 standard). This bit is used by the LLC in the busy/retry state machine.
1 Subaction gap Indicates that the PHY has detected that the bus has been idle for a subaction gap time (as defined in the
IEEE 1394-1995 standard). This bit is used by the LLC to detect the completion of an isochronous cycle.
2 Bus reset Indicates that the PHY has entered the bus reset state.
3 Interrupt Indicates that a PHY interrupt event has occurred. An interrupt event may be a configuration time-out, a
cable-power voltage falling too low, a state time-out, or a port status change.
4-7 Address This field holds the address of the PHY register whose contents are being transferred to the LLC.
8-15 Data This field holds the register contents.
00
(a)
01
(b)
00
00 S[14:15]S[0:1]
D0, D1
CTL0, CTL1
SYSCLK
00
Figure 17. Status Transfer Timing