122 Keysight E1458A 96-Channel Digital I/O Module User GuideKeysight E1458A Register Information Addressing the RegistersThe Base AddressWhen you are reading or writing to a module register, a hexadecimal or decimalregister address is specified. This address consists of a base address plus aregister offset. The base address used in register-based programming dependson whether the A16 address space is outside or inside the Keysight E1405/E1406Command Module.A16 Address Space Outside the Command ModuleWhen the Keysight E1405/E1406 Command Module is not part of your VXIbussystem (Figure B-1), the Keysight E1458A’s base address is computed as:C00016 + (LADDR * 40)16or (decimal)49,152 + (LADDR * 64)where C00016 (49,152) is the starting location of the register addresses, LADDRis the module’s logical address, and 64 is the number of address bytes per VXIdevice. For example, the E1458A’s factory-set logical address is 144 (9016),therefore it will have a base address of:C00016 + (9016 * 4016) = C00016 + 240016 = E40016or49,152 + (144 * 64) = 49,152 + 9216 = 58,368A16 Address Space Inside the Command Module or MainframeWhen the A16 address space is inside the Keysight E1405/E1406 CommandModule (Figure B-2), the module’s base address is computed as:1FC00016 + (LADDR * 40)16or2,080,768 + (LADDR * 64)where 1FC00016 (2,080,768) is the starting location of the VXI A16 addresses,LADDR is the module’s logical address, and 64 is the number of address bytesper register-based device. Again, the Keysight E1458A’s factory-set logicaladdress is 144. If this address is not changed, the module will have a baseaddress of:1FC00016 + (9016 * 6416) = 1FC00016 + 240016 = 1FE40016or2,080,768 + (144 * 64) = 2,080,768 + 9216 = 2,089,984
