Sundance SMT329 - Manual (Page 21)

4.3 TIM Global Bus Resources
There are three main global bus resources available to TIMs on this motherboard. These are
the 32 bit VME bus, the 8 Megabyte static ram (sram), and the board control registers.
The VME bus is directly accessible to the TIMs without reducing the availability of the sram
to any other internal sram requestor.
The TIMs can access the sram with zero wait states for burst transfers, after arbitration for
the sram bus.
Access to the global resources is selected by an arbitration state machine. Resources remain
granted to the last resource master after the cycle has finished so that contiguous transfers
proceed without further arbitration. Arbitration only occurs when two (or more) possible bus
masters are requesting the same resource.
Because the TIMs have direct access to the VME bus, the risk of deadlock that was present in
the SMT328 is now removed. This is because the VME bus arbiter, on another VME bus
board, is the only arbiter in the path to granting bus master access to the VME bus for the
TIM, whereas on SMT328 the VME bus arbiter and the sram bus arbiter both had to grant
access.
User Manual SMT329 Page 21 of 52 Last Edited: 09/02/2007 10:58:00