CAEN
Electronic Instrumentation
UM5175
–
V2495/VX2495 User Manual rev. 1
34
9
Communication Interfaces
The V2495 board can be accessed via both VME bus or USB interface. All registers are accessible from both
communication interfaces (VME/USB).
9.1
VME Bus
The V2495/VX2495 boards can be individually addressed on the bus by means of their assigned base address.
The base address is set by means of on-board rotary switches (see Sect.
) for all VME
accesses except for geographical addressing.
Geographical addressing is only supported on VX2495 modules inserted in VME64X crates: the module Base
Address(BA) is automatically set by the position of the module in the crate. Geographical Address (GA) will set
BA[23:19].
Geographical addressing is only supported with address modifier (AM) for CR/CSR space (0x2F).
The geographical address corresponds to the slot identification number of the standard VME crate (1 is the leftmost
slot; 21 is the rightmost slot). VX2495 module inserted in slot 3, for instance, could be accessed with 0x2F address
modifier at base address equal to 0x180000.
Registers can all be accessed via VME bus in A24/A32 addressing mode and D32 mode.
VME interface supports interrupt generation requested by the User PFGA: User FPGA can generate an interrupt
request by asserting its nINT signal (active low). The interrupt will be generated only if the appropriate registers have
been configured (see
USB and VME cycles cannot be performed at the same time. It is up to the user to guarantee that each bus cycle is
mutually exclusive.
9.2
USB
USB interface grants access to the same address space and corresponding registers of the VME interface.
Register access over USB must be performed with Base Address equal to 0. The BA parameter in any of the following
register tables is assumed to be zero for USB accesses.