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Reading the Data
Register
As shown in Figure 3-12, the digitizer’s data register is mapped into the
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 + 02
16
) is set high (’1’). The
partition window delay is monitored by reading bit 1 of the arm status
register (base +43
16)
, 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