The module can work in a “multimaster” system with the possibility of operating as a system controller, in this case (which is the default option as the board is inserted in the slot 1), it works as Bus Arbiter, Sysclock Driver, IACK Daiy Chain Driver, etc.
The module features a LED display which allows to monitor the VME bus activity in detail. The front panel features 5 TTL/NIM programmable outputs on LEMO 00 connectors (default assignment is: DS, AS, DTACK, BERR signals and the output of a programmable Location Monitor) and two programmable TTL/NIM inputs (on LEMO 00 connectors).
The V2718 accepts BERR or DTACK as cycle terminations. BERR is handled as cycle termination whether it is produced by the V2718 itself or by another board. The Status word broadcasted as the cycle is acknowledged, informs the PC HOST about the cycle termination type (BERR or DTACK*).
A programmable bus timer allows users to select a VMEbus time-out period. The time-out period is programmed through the Bus Timeout bit in the Control register ( = 0 → timeout = 50 μs; = 1 → timeout = 400μs). The VMEbus Timer module asserts BERR if a VMEbus transaction times out (indicated by one of the VMEbus data strobes remaining asserted beyond the time-out period).
插件侧面可调节位置由上往下有 Firmware Sel.(STD BKP)、Base address selection、DIP switches(0,1,2,3,4)、I/O(NIM TTL)、A2719 Firmware Sel.(STD BKP).
其中 DIP switches 可选择通过System Control。Status register(Base Address + 0x00, D16, read/write) This register contains information on the status of the module.
The V2718 front panel houses 7 LEMO 00 type connectors, 5 outputs and 2 inputs; signals can be either NIM or TTL (dip-switch selectable). Seven green LEDs (one per connector) light up as the relevant signal is active. All the signals can perform several functions, default setting of the output signals is:
- DS (either DS0 or DS1)
- LMON (output of Location Monitor)
The V2718 monitors the cycles on the bus, whether they are held by itself or by other masters, and produces a Trigger Out LMON signal as soon as a particular cycle is performed. The LMON out is available by default as front panel signal.
System Controller Functions
When located in Slot 1 of the VME crate, the V2718 assumes the role of SYSTEM CONTROLLER and sets the SYSTEM CONTROLLER status bit in the STATUS register.
In accordance with the VME64 specification, as SYSTEM CONTROLLER the V2718 provides:
- a system clock driver,
- an arbitration module,
- an IACK Daisy Chain Driver (DCD)
- a bus timer.
The V2718 provides a 16.66 MHz SYSCLK signal when configured as System Controller.