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The TRANSFER Program
12.4 IF SOMETHING GOES WRONG
Ordinarily, THAMSFEFRand "FEF 288 should be able to stop in an orderly manner if data transfer
cannot proceed normally.
Specifically, if TFEHAHMH=FEF cannot read the data file, it will send a signal
terminating #FERZEE, Likewise, if "FEF ZEB receives invalid data, it will send a signal terminating
TEAHSFER.
Sometimes one of the programs may terminate without being able to send a signal to the other, leaving the
other program hanging. For example, if /<F EF ZEKE! cannot create a vector, it will stop without sending
any signal to TEHHZFER.
If one program terminates without stopping the other, the following
procedures can be used to regain control of the hung program:
o If "FERZEE stops without terminating |FHMHZF ER, halt TEHM=FER by pressing
twice
and restore the loop by performing RESET HFIL and RESTORE IQ on the HP-71.
o If THHM=FEF stops without terminating "FEF ZEIE try halting #=FERZEHE by pressing
PAUSE. Failing that, use CLR I/0.
Failing that, the program can be stopped with RESET
(shift PAUSE).
12.5 HANDLING OF NUMERIC EXCEPTIONS
Normally, extremely large numbers, extremely small numbers, and NaNs* will not occur when using the
HP 3421A Data Acquisition/Control Unit.
It is possible, however, for a custom conversion program to
generate numbers out of the normal range of the HP 3421A.
Under these circumstances, TRANSFER
will make the following conversions for compatibility with the Series 200 computers:
e If a value being transferred has an absolute value greater than 1.0E+308 TRANSFER will
replace it with *1.0E+308. This will also occur for a value of [rit
e If a value being transferred has an absolute value less than 1.0E-307, TRANSFER will
replace it with O.
o If a value being transferred is NaN, TRANSFER will replace it with the value 9999999999.
This is in keeping with the HP 3421 A method of representing out-of-range readings. (Note
that, except in the case of unusual activity in a custom conversion program, a value of NaN
will never occur.)
*A NaN (Not-a-Number) is a special value generated to conform to the IEEE proposal for floating-point
arithmetic. It is explained more fully in the HP~-71 Owner's Manual.
12-6
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