Datasheet

8–4
packet to be transmitted and then a bus reset initiated so as to verify that all nodes on the bus have updated their
RHBs and Gap_Count values, without having the Gap_Count set back to 63 by the bus reset. The subsequent
connection of a new node to the bus, which initiates a bus reset, then causes the Gap_Count of each node to be set
to 63. Note, however, that if a subsequent bus reset is instead initiated by a write to register 1 to set the IBR bit, all
other nodes on the bus have their Gap_Count values set to 63, while this node Gap_Count remains set to the value
just loaded by the write to PHY register 1.
Therefore, in order to maintain consistent gap-counts throughout the bus, the following rules apply to the use of the
IBR bit, RHB, and Gap_Count in PHY register 1:
• Following the transmission of a PHY-config packet, a bus reset must be initiated in order to verify that all
nodes have correctly updated their RHBs and Gap_Count values and to ensure that a subsequent new
connection to the bus causes the Gap_Count to be set to 63 on all nodes in the bus. If this bus reset is
initiated by setting the IBR bit to 1, the RHB and Gap_Count field must also be loaded with the correct values
consistent with the just transmitted PHY-config packet. In the TSB43AB23 device, the RHB and Gap_Count
are updated to their correct values upon the transmission of the PHY-config packet, so these values may
first be read from register 1 and then rewritten.
• Other than to initiate the bus reset, which must follow the transmission of a PHY-config packet, whenever
the IBR bit is set to 1 in order to initiate a bus reset, the Gap_Count value must also be set to 63 so as to
be consistent with other nodes on the bus, and the RHB must be maintained with its current value.
• The PHY register 1 must not be written to except to set the IBR bit. The RHB and Gap_Count must not be
written without also setting the IBR bit to 1.
8.4 EMI Guidelines
For electromagnetic interference (EMI) guidelines and recommendations send a request via e-mail to
1394–[e-mail].