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The Register Offset
and Register Number
External Computer
Programming
Appendix C
Depending on whether absolute addressing or select code 8 is used, either a
register offset or register number is specified as part of the register address.
Absolute addressing specifies a register offset, which is the register's
location in the block of 64 address bytes. For example, the AFG's
Command Register has an offset of 08
this register, the offset is added to the base address to form the register
address (using a logical address of 80):
register address = base address + register offset
or
Using select code 8 requires that you specify a register number. The
register number is the register offset/2. Referring to Figure C-1A, the
Command Register with an offset of 08, is register number 4.
Note
The example programs found in this appendix are IBASIC programs using
absolute addressing.
When the AFG is programmed by an external computer through the
E1300/E1301 mainframe or E1405/E1406 Command Module, the registers
are accessed using
.
VXI:WRITE
DIAG:PEEK?/DIAG:POKE and VXI:READ?/VXI:WRITE
Throughput speed using
VXI:READ?
(including the A16 starting location 1FC000
and
VXI:WRITE
Thus, the E1300/01/E1405/06 processor must calculate the complete
register address which decreases throughput speed.
IBASIC programming using absolute addressing or select code 8 is faster
than either
DIAG:PEEK?
because the registers are accessed from the VXIbus backplane rather than
from the HP-IB. Also,
= 1FC000
+ (80 * 64)
16
= 1FC000
+ 1400
16
= 2,080,768 + (80 * 64) + 8
= 2,080,768 + 5120 + 8 = 2,085,896
and
DIAG:PEEK?
DIAG:PEEK?
and
VXI:WRITE
because the complete register address
specify the device logical address and register offset only.
and
DIAG:POKE
and
READIO
HP E1340A Register-Based Programming 233
. When you write a command to
16
+ 08
16
16
+ 08
= 1FD408
16
16
16
, or
DIAG:POKE
VXI:READ?
and
is faster than
DIAG:POKE
) is specified.
16
or
VXI:READ?
and
are not parsed.
WRITEIO
and
VXI:READ?
VXI:WRITE
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