The HP48SX Print Trace system provides a facility for the HP48SX externally
similar to the built-in print trace feature of the HP28C and HP28S. This
facility of the 28s allows you to trace almost all calculator operations to
an 82240A or 82240B thermal printer. The HP48SX provides no native print
trace feature, but does provide a generalized facility called "Vectored
ENTER" which I have used to implement this system. Note that my output
format is almost identical to that of the HP28 series calculators. I chose
this format for consistency, not because I find it aesthetically pleasing.
This system can be modified by the user to print in almost any format
desired.
PROCEDURE
---------
1. Using Kermit, load TRAC into the HOME directory. For your reference,
the BYTES command yields a checksum of # D720h and a size of 780.5
bytes.
2. Optional: Put 'TRAC' on stack level 2 and 81.2 on stack level 1. Go to
the right-shift-MODES menu and hit ASN. This will assign TRAC to user
keyboard position 81.2, or left-shift-right-shift. In other words, if
the HP48SX is in user mode, hitting the orange key followed by the blue
key will evaluate the TRAC function. To put your calculator into user
keyboard mode, hit left-shift-USR twice. If you are successful, the
USER annunciator will appear just below the top line of the display.
3. To toggle between tracing mode and normal mode, either type TRAC, hit
the TRAC key from the HOME menu or, if you've performed optional step
2. above, do a left-shift-right-shift (orange followed by blue).
Either "Print trace on." or "Print trace off." will appear at the top
of the stack display as appropriate.
SYSTEM DESCRIPTION
------------------
IMPORTANT NOTE: in this document, [alpha] refers to the greek lowercase
alpha which is accessed in alhpa mode, right-shift A and [beta] refers to
the greek lowercase beta which is accessed in alpha mode right shift B.
For example, if I mention a variable named '[beta]ENTER', to type the name
you would hit the apostrophe key followed by the alpha key twice (to put
the calculator in alpha mode) followed by right-shift B followed by E, N,
T, E and R.
This Print Trace system uses an as-yet undocumented facility called
"Vectored ENTER." The only reference so far to this facility is in
Appendix E of the HP48SX Owner's Manual. This states that when flag -63 is
set, User-defined ENTER is activated. I am indebted to Ron at the Hewlett-
Packard Calculator Support department, Corvalis, OR for explaining it
further. To summarize his explanation and my findings:
If "Vectored ENTER" mode (flag -63) is set and the calculator is in
USER (NOT 1USR) mode (via the keyboard or setting flag -62)
AND There is a variable named '[alpha]ENTER' in the current path,
BEFORE any operation, whenever the command line would normally
be pushed to the stack, it is pushed to stack level 1 delimited
by " characters on either end instead. Following this action,
the variable named '[alpha]ENTER' is evaluated. Typically
[alpha]ENTER would be a program. If the contents of the
command line are not a single string, this action causes the
entire command line to be placed on the stack as a single
string. If it was already a string, it winds-up on the stack
with an extra set of delimiting " characters. This means that
if either the OBJ-> or STR-> command is executed in the
[alpha]ENTER program, the stack will contain precisely what it
would have if the calculator were not in Vectored ENTER mode.
AND/OR There is a variable named '[beta]ENTER' in the current path,
AFTER any operation is performed, the name of the operation is
placed on stack level 1 as a string. PURGE and ENTER itself
are represented by the null string (""). If, however, ENTER is
acting as DUP, "DUP" is returned. If the operation is
unsuccessful, its name is not placed on the stack. Menu
navigation is not reported, but path navigation is.
The TRAC function checks a list in the home directory with the name
'[alpha][beta]FG'. If the first element of the list indicates that tracing
is off (or the list doesn't exist), tracing is turned on and that fact is
indicated in the first element of the list. If the first element of the
list indicates that tracing is on, it is turned off and similarly noted.
When tracing is turned on, the state of flag -62 is indicated in element 2
of the '[alpha][beta]FG' list. When tracing is turned off, the former
state of flag -62 is restored. In other words, if the calculator was in
USER mode when tracing was turned on, it is left in USER mode when it is
turned off. If the calculator was not in USER mode when tracing was turned
on, it is taken out of USER mode when tracing is turned off. This is
necessary since the Vectored ENTER mode is only effective if the calculator
is also in USER mode. To turn tracing on, TRAC sets flags -62 and -63 and
places programs in variables named '[alpha]ENTER' and '[beta]ENTER' in the
HOME directory. To turn tracing off, TRAC clears flag -63 and when
appropriate clears flag -62 and purges the variables named '[alpha]ENTER'
and '[beta]ENTER' from the home directory.
The [alpha]ENTER program simply makes a copy of the command line as a
string padded on the right with a blank in variable [alpha][beta]ENTER and
executes the OBJ-> command to leave the stack in the same state it would
have been in had Vectored ENTER not been in effect.
The [beta]ENTER program concatenates the current function to the end of the
command line saved in [alpha][beta]ENTER and prints it. If there is no
variable [alpha][beta]ENTER, this means that there was no command line and
[beta]ENTER simply prints the operation. After it has done this,
[beta]ENTER prints level 1 of the stack prefixed by the characters "1: "
unless the stack is empty, in which case it prints the character string
"[Empty Stack]". [beta]ENTER then prints 0000300000081000000810000000700000060000000081FFFFF1000000000EFFFF300000000000EFF7000000
GROB 64 64 0000006FF700000000000EDBFF30000000008BFFFFF100000000FEFFFFF700000008FFFFFFFF100000067FFFFFFF3000000BFFFFFFFFF0000089FFFFFFFFF100006CFFFFFFFFF300003FFFFFFFFFF700089FFFFFFFFFFF0008C7DFFFFFFFFF100CCF7FFFFFFFFF3006CF3EFFFFFFFF300BEFB3EFFFFFFF7001FFFFFFFFFFFF708DFFFFFFFFFFFFF08CFFFFFFFFFFFFF14EFFFFFFFFFFFFF14EFFFFFFF3EFFFF16FFFFFFFF3CFFF722FFFFF7FF10F7F736FFFFFFFF10F3E77EFFFFFFF300F1E779FFFFFFF400E1A769FFFFFFFF00 nothing when you turn tracing on and
prints TRAC when you turn it off.
If you find any other differences or problems, please post them as
responses to this entry. If you have any questions, don't hesitate to call
