User`s guide

The XMI

2.3 Arbitration Cycles

The XMI protocol includes arbitration because, at any time, any

or all of the nodes may desire the use of the XMI. Arbitration

determines which node gains the XMI when more than one node

requests the XMI simultaneously. Arbitration cycles occur in

parallel with data transfer cycles, since the XMI has a set of

arbitration-dedicated lines.

Figure 2–6 XMI Arbitration Block Diagram

XMI HOLD L

XMI SUP L

XMI CMD REQ[1] L

Node

Central

Arbiter

msb−p168−89

XMI RES REQ[1] L

Node

XMI GRANT[1] L

XMI CMD REQ[14] L

XMI RES REQ[14] L

XMI GRANT[14] L

2–20