Reading the Data As shown in Figure 3-12, the digitizer’s data register is mapped into the Register HP E1406 Command Module’s A24 address space. A command used to

read the data register is the Command Module command:

DIAGnostic:PEEK? <address >, <width >

<address >: the address (A24 base + offset) of the data register

<width >: the number of bits per digitizer reading. For the VME transfer modes, width is 16 (bits) with the exception of modes "MEMory:BOTH32" and "CONVerter:BOTH32", which are 32 bits. The HP E1406 Command Module cannot do 32-bit transfers to/from the VME (VXI data transfer) bus. However, 32-bit transfers at approximately 8 MByte/ second transfer rates are possible using an embedded controller.

Note Additional information on the Command Module’s DIAGnostic:PEEK? command is located in the HP E1406 User’s Manual. Chapter 2 "Using the Digitizer" contains examples of 16-bit and 32-bit data transfers using an embedded PC.

VME Bus Data Format Data is transferred (real time or post measurement) over the VME bus in the digitizer’s packed (A/D) format. Data in this format are left-justified, signed 2’s complement numbers . See "Packed Reading Conversions" on page 134 for information on converting the readings to voltages.

Segmented Reading Transfers

Multiple arms (bursts) of pre-arm and post-arm readings segment digitizer memory (Figure 3-13). Real time and post measurement transfers of segmented readings are also achieved by reading the data register. For high-speed configurations such as those which use an embedded controller, the time at which post measurement readings can be retrieved and a delay (partition window) while the digitizer sets up the next memory segment for reading storage and retrieval must be accounted for (Figure 3-13). Post measurement readings (either segmented or non-segmented) can be retrieved when bit 4 of the traffic register (base + 0216) is set high (’1’). The partition window delay is monitored by reading bit 1 of the arm status register (base +4316), or by reading bit 9 (READy) of the digitizer’s Condition register in the Operation Status Group (page 169). For real time transfers, monitoring either partition window bit is best accomplished when the arm source is immediate (ARM:STARt:SOURce IMMediate).

Chapter 3

Understanding the HP E1429 Digitizer 153

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HP E1429A manual Segmented Reading Transfers