Trigger Pull Up Trigger signals output from the E8491A ‘Trig Out’ port can be “pulled up” to +30V as shown in Figure
+V = pull up voltage (+30V max)
Output trigger state LH = normally low, high true
Output trigger state HL = normally high, low true (default)
Figure 3-2. Using a Pull Up on the HP E8491A ‘Trig Out’ Port.
Using HP E8491A Shared Memory
Locating E8491A Shared Memory
The E8491A has 128 kBytes of shared (VME) memory. This memory is in the E8491A’s A24 address space and is available to those VXI instruments capable of mapping and accessing A24 memory. Shared memory is often used as a temporary storage space for data transfers between the PC and VXI instruments.
HP instruments with the ability to store and receive data from shared memory generally implement the SCPI (Standard Commands for Programmable Instruments) MEMory:VME subsystem shown below:
MEMory:VME:SIZE
MEMory:VME:ADDRess
MEMory:VME:STATe
Corresponding HP VXIplug&play functions are:
hpexxxx_memVmeAddr hpexxxx_memVmeSize hpexxxx_memVmeStat
where xxxx is the instrument model number.
In order to use the E8491A shared memory, you must first locate the starting address of the memory as mapped by the resource manager (see “Running the Resource Manager” in Chapter 2). The address varies from system to system depending on the number of devices that use A24 memory. The address can be determined programatically using HP VISA or SICL, or by viewing the resource manager output. Each method is described in the following sections.
Chapter 3 | VXI Programming Using the IEEE 1394 Serial Bus 47 |