VXI manual The VT1433B VXI Device, Address Space, Shared Memory, Memory Map

VT1433B User's Guide

Module Description

The VT1433B VXI Device

Address Space

The VXI system architecture defines two types of address space. A16 space consists of 64 kBytes and A24 consists of 16 MBytes.

The VT1433B has a 32-bit port through which it has access to the A16 and A24 space. It can also use D32 to send and receive data though the port. Or it can use the port for 16-bit data transfers by using only 16 of the 32 bits available.

The VT1433B performs a different type of VME cycle depending on the number of bits transferred per cycle (two cycles for 16-bit transfers and one cycle for 32-bit).

Shared Memory

Shared memory provides a way for the VT1433B to transfer data to a controller. The shared memory in the VT1433B is mapped to the A24 VXI address space. The controller can then access that same address space to receive or write data. A function can be called to retrieve the data. See the chapter on “The Host Interface Library.”

Memory Map

The following discussion of memory mapping is included as supplemental information. It is not needed to operate the VT1433B because this functionality is hidden when using the VT1432A Host Interface Library software.

Refer to the VT1433B block diagram (Figure 5-1). The VXI interface maps some of the VT1433B’s B-bus internal memory space so that it is visible to the VXI Bus. The port connecting the A and B busses also allows the VXI Bus access to the SRAM, DRAM and inputs which are on the A bus. (SRAM stands for Static RAM; DRAM is Dynamic RAM.)

The VXI interface has two “windows” on the B bus memory space. Each is 512 kbytes, which is 128 32-bit words. One of the windows is fixed and the other is movable. The movable window allows the VXI Bus access to many different parts of the memory space. The fixed window contains:

￿The A16 registers

￿The B-bus SRAM

￿The hardware registers

￿The FIFO (which is in DRAM)

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