TSB41AB3IPFP datasheet(27/52 Pages) TI

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TSB41AB3

IEEE 1394a2000 THREEPORT CABLE TRANSCEIVER/ARBITER

SLLS418I − JUNE 2000 − REVISED DECEMBER 2004

POST OFFICE BOX 655303

• DALLAS, TEXAS 75265

APPLICATION INFORMATION

using the TSB41AB3 with a lower-speed link layer (continued)

To assist in building an accurate speed-map, the TSB41AB3 has the capability to indicate a speed other than

S400 in its transmitted self-ID packet. This is controlled by the Link_Speed field in register 8 of the

vendor-dependent page (page 7). Setting the Link_Speed field affects only the speed indicated in the self-ID

packet; it has no effect on the speed signaled to peer PHYs during self-ID. The TSB41AB3 identifies itself as

S400 capable to its peers regardless of the value in the Link_Speed field.

Generally, the Link_Speed field is not changed from its power-on default value of S400 unless it is determined

that the speed-map (if one exists) is incorrect for path entries terminating in the local node. If the speed map

is incorrect, it can be assumed that the bus manager has used only the self-ID packet information to build the

speed map. In this case, the node may update the Link_Speed field to reflect the lower speed capability of the

LLC and then initiate another bus-reset to cause the speed-map to be rebuilt. Note that in this scenario any

speed-map entries for node-to-node communication paths that pass through the local node’s PHY are restricted

by the lower speed.

In the case of a leaf node (which has only one active port) the Link_Speed field may be set to indicate the speed

of the LLC without first checking the speed-map. Changing the Link_Speed field in a leaf node can only affect

those paths that terminate at that node, because no other paths can pass through a leaf node. It can have no

effect on other paths in the speed map. For hardware configurations that can only be a leaf node (all ports but

one are unimplemented), it is recommended that the Link_Speed field be updated immediately after power-on

or hardware reset.

power-up reset

To ensure proper operation of the TSB41AB3 the RESET terminal must be asserted low for a minimum of 2 ms

from the time that PHY power reaches the minimum required supply voltage. When using a passive capacitor

on the RESET terminal to generate a power-on reset signal, the minimum reset time is assured if the value of

the capacitor has a minimum value of 0.1

µF and also satisfies the following equation:

Cmin = 0.0077 × T + 0.085

where Cmin is the minimum capacitance on the RESET terminal in µF, and T is the VDD ramp time, 10%–90%,

in ms.

crystal selection

The TSB41AB3 and other TI PHY devices are designed to use an external 24.576 MHz crystal connected

between the XI and XO terminals to provide the reference for an internal oscillator circuit. This oscillator in turn

drives a PLL circuit that generates the various clocks required for transmission and resynchronization of data

at the S100 through S400 media data rates.

A variation of less than

±100 ppm from nominal for the media data rates is required by IEEE Std 1394. Adjacent

PHYs may therefore have a difference of up to 200 ppm from each other in their internal clocks, and PHYs must

be able to compensate for this difference over the maximum packet length. Larger clock variations may cause

resynchronization overflows or underflows, resulting in corrupted packet data.

For the TSB41AB3, the SYSCLK output may be used to measure the frequency accuracy and stability of the

internal oscillator and PLL from which it is derived. The frequency of the SYSCLK output must be within

±100 ppm of the nominal frequency of 49.152 MHz.

TSB41AB3IPFP Datasheet(PDF) 27 Page - Texas Instruments

TSB41AB3IPFP Datasheet(HTML) 27 Page - Texas Instruments

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