Maximum Latency

Maximum Latency

The worst-case delay for the start of a VME access, if all of the devices on the IO4 simulataneously request the IO channel for a 128 byte write and the VME adapter receives the grant last, the VME access start could be delayed for a total of about 2 microseconds. Only a VME read would suffer this delay; a VME write would not.

There is a another potential delay from an independent cause, which depends on the number of bus master (IO4 and CPU) boards on the system bus. If all the E-bus masters in a fairly large configuration hit the bus at once, a VME read or write could be held up by as much as 1 microsecond in a large system.