Datasheet

TSB81BA3D, TSB81BA3DI

IEEE 1394b THREE-PORT CABLE TRANSCEIVER/ARBITER

SLLS559E − DECEMBER 2002 − REVISED JUNE 2006

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

APPLICATION INFORMATION

Table 4. Page 0 (Port Status) Register Field Descriptions (Continued)

FIELD SIZE TYPE DESCRIPTION

Max_port_speed 3 Rd/Wr Max_port_speed

The maximum speed at which a port is allowed to operate in beta mode. The encoding is:

000 = S100

001 = S200

010 = S400

011 = S800

100 = S1600

101 = S3200

110 = reserved

111 = reserved

An attempt to write to the register with a value greater than the hardware capability of the port results

in the maximum value that the port is capable of being stored in the register. The port uses this

maximum speed capable of the port. Software may modify this value to force a port to train at a lower

than maximum, but no lower than minimum speed.

LPP

(Local_plug_present)

1 Rd This flag is set permanently to 1.

Cable_speed 3 Rd This variable is set to the maximum speed that the port is capable of. The encoding is the same as

for Max_port_speed.

Connection_unreliable 1 Rd/Wr If this bit is set to 1, then a beta mode speed negotiation has failed or synchronization has failed. A

write of 1 to this field resets the value to 0.

Beta_mode 1 Rd Operating in beta mode. If this bit is 1, the port is operating in beta mode; it is equal to 0 otherwise

(that is, when operating in 1394a−2000 mode, or when disconnected). If Con is 1, RxOK is 1, and

Beta_mode is 0, then the port is active and operating in the 1394a−2000 mode.

Port_error 8 Rd/Wr Incremented whenever the port receives an invalid codeword, unless the value is already 255.

Cleared when read (including being read by means of a remote access packet). Intended for use

by a single bus-wide diagnostic program.

Loop_disable 1 Rd This bit is set to 1 if the port has been placed in the loop disable state as part of the loop free build

process (the PHYs at either end of the connection are active, but if the connection itself were

activated, then a loop would exist). Cleared on bus reset and on disconnection.

In_standby 1 Rd This bit is set to 1 if the port is in standby power-management state.

Hard_disable 1 Rd/Wr No effect unless the port is disabled. If this bit is set to 1, the port does not maintain connectivity status

on an ac connection when disabled. The values of the Con and RxOK bits are forced to 0. This flag

can be used to force renegotiation of the speed of a connection. It can also be used to place the

device into a lower power state since when hard disabled, a port no longer tones to maintain 1394b

ac-connectivity status.