DS3875 datasheet(11/58 Pages) NSC

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40 DS3875 Interfaces (Continued)

TLH10747 – 5

FIGURE 3

When competing the DS3885 Arbitration Transceiver is en-

abled to place the competition numbers CN(7

0) and its

associated parity bit CNp onto the Futurebusa backplane

During every cycle whether or not competing the winning

module’s

arbitration

number

read

the

value

WIN

GT signal and PER signal is determined and up-

dated in the appropriate internal registers

The host can read or write (RW) into the Arbitration Con-

troller registers to change the controller configuration

check status or RW a new arbitration numbermessage

The host can select to latch data either on the falling edge

of DSACK

or on the rising edge of CS

by releasing or

asserting the SEL pin

The Module may become bus master during Phase 5 if the

normal arbitration cycle was successful Phase 0 if Parking

was successful or Phase 2 if IBA was successful Upon

becoming bus master the Arbitration Controller will issue

BGRNT

This signal indicates to the Protocol Controller

that it can now perform the desired transactions on the Par-

allel addressdata bus

The Protocol Controller will let the Arbitration Controller

know if it has locked resources by asserting the LKD sig-

nal If resources were locked then at transfer of tenure the

Arbitration Controller will issue UNLK to the Protocol Con-

troller to unlock resources

A dummy cycle will be initiated by the Arbitration Controller

to perform the unlocking function if lock (LKD ) is still as-

serted after end of tenure (ENDT ) is asserted and no other

modules are competing Unlock will be asserted at the

transfer of bus tenure (even if this module wins the competi-

tion) If another module initiates arbitration competition this

module will participate in the competition and will issue the

unlock (UNLK ) signal upon transfer of bus tenure When

the bus transaction is complete and no resources are

locked the Protocol Controller has the option of enabling

either Idle Bus Arbitration or parking (IBA

PK in CTRL3)

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