When a message is received the FIFO strobe (FSTR ) will

be negated strobing a new message into the external FIFO

given the following conditions

1 The message is not being sent by this module

2 This is the second pass of an arbitration message

3 No errors occurred during this arbitration cycle

4 This is not a powerfail interrupt message ( PFINT )

Once all the modules have negated AQ

upon receiving

AQI the arbitration cycle will transition to Phase 0

TLH10747 – 16

FIGURE 7a DS3875 Phase 0 Arbitration State Diagram

Note

HALT is assumed to be negated in this state diagram Also the arbitration Controller GO bit in CTRL3 register must be asserted for the controller to

accept requests Otherwise this module may not compete but will be a by-stander

Note 1

Idle Bus Arbritation during Phase 0 is not an internal state of the Arbitration Controller It is shown in this state diagram only to give a better understanding

of Phase 0 arbitration

Note 2

The Arbitration Controller does not check for LKD

was asserted during IBA another module could win IBA and try to access this modules locked resources this would result in deadlock Also the Arbitration

controller does not check AS

DS

DI

this is left up to external logic and this must be the first pass if two pass arbitration has been selected

Note 3

The output di from this module is driven from external control logic it is only shown in this diagram to allow a clearer understanding of how IBA relates to

normal arbitration

Note 4

Note that message request (MGRQ ) has a higher priority inside the arbitration controller then does bus request (BRQ )

Note 5

This is a dummy arbitration cycle initiated to unlock (UNLK ) the modules resources The dummy cycle is initiated by the current master if the modules

resources are still locked ( LKD ) after end of tenure (ENDT ) has been issued ( BGRNT

MasterLKD

ENDT ) and the arbitration bus is idle

Note 6

If this is the second pass of a two-pass arbitration cycle and a new request ( BRQ or MGRQ ) is generated that request will not be allowed to compete

until the next arbitration cycle Note that pre-emption is allowed

Note 7

If Two-Pass arbitration has been selected Parking is only possible during Phase 0 of the first pass

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