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10,7/unscsp/bootdx/a8ddt.mem
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A8DDT.RNO Version 1
1.0 SUMMARY
A8DDT is a TECO macro which allows use of basic File DDT functions
on A8 format files, particularly the DX10 microcode. This
provides a means to inspect and patch the A8 file prior to loading
it into the PDP-8. The code operates only in octal type in/out
mode and is intended for use by experienced systems programmers
and DEC service personnel.
2.0 INITIALIZING A8DDT
A8DDT IS A TECO macro which is started in the following manner:
.R TECO
*ERA8DDT.TEC$YAHXAMA$$
at this point control will be transferred to A8DDT's
initialization code which will prompt with
FILE:
Answer this prompt with the full file spec of the A8 file you wish
to use. A8DDT will accept any file spec construct which would be
accepted by TECO including SFD's. The file spec must be
terminated with a carriage return. While accepting your file spec
A8DDT allows use of <DEL>, ^U, and ^R for editing. When your file
spec has been accepted A8DDT will respond with
A8DDT <cr><lf>
to let you know it is ready to accept commands.
3.0 A8DDT COMMANDS
A8DDT is a subset of DDT which operates exclusively in octal type
in/out mode. The following commands are accepted:
n/ open location n (up to 4 digits) and display its
contents
./ display the contents of the last opened location
<cr> close the location and store any numeric supplied (up to
4 digits) as the new contents
<lf> perform <cr> processing and then open the next
consecutive location
<del> delete the last numeric argument typed
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? enter/exit debug (this is used to activate TECO's ? mode
mode for tracing the macro's operation)
^Z exit the program (A8DDT will close the edited file and
produce a backup file)
4.0 INTERNALS INFORMATION
The following information is not necessary for use of A8DDT but
may be helpful to those wishing a better understanding of the
program and its operational peculiarities.
4.1 A8 FILE FORMAT
A8 files are produced by the CONVRT program (diagnostic DDQDG)
from BIN files output by PAL10. The files are in the following
format:
8 wc,adr,12,12,12, . . . . .12,cks
8 wc,adr,12,12,12, . . . . .12,cks
8 0,adr,cks
where:
8 pdp-8 file identifier
space,sifnifies asciized file
wc word count
adr load address
12 up to 2 characters for each 12-bit data word
cks file line checksum
<cr><lf> indicates end of line
As many line of this type as required to load the PDP-8 file are
in the file followed by the EOF indicator:
8 PDP-8 identifier
space,signifies asciized file
0 word count of 0 signifies transfer block
adr PDP-8 start address
cks file line checksum
<cr><lf> indicates end of line
The file line checksum is the 12-bit negated checksum. The word
count, the load address, the data, and the line checksum added
together produces a 12-bit zero sum.
4.2 SPECIAL CONSIDERATIONS
A8DDT does not support the A8 "octal file format" option. The
decision to impose this restriction was based on two factors.
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First, no currently available or planned software produces this
format. Second, this format was intended to allow patch overlays
which could not be handled by A8DDT without significantly
degrading response.
A8DDT was designed to be easily modified to handle other
"asciized" formats. To do this the references to the A8
identifier "8" would have to be changed. These occur at tag
EXAMINE-T+1 line where <cr><lf>8 is searched, at tag CRLF+2 lines
where 8<space>, is searched, and at tag CRLF+3 lines where a blank
entry is created. All occurances of ^O7777 would also have to be
changed to mask the word length for the corresponding processor.
4.3 Q-REGISTER USEAGE
The following defines the standard Q-register use within A8DDT:
A Code. Holds the A8DDT macro itself.
C Data. Used to pass arguments to subroutines.
Usually contains the contents of currently open
location.
D Code. Subroutine to convert numeric in Q-register C to
A8 format and store at the current pointer position.
E Code. Subroutine to type the contents of Q-register 1.
F Flag. Indicates a location is currently opened.
G Flag. Indicates a numeric argument was the last thing
typed.
I Code. Subroutine to convert the asciized data at the
current pointer position to binary and return result in
Q-register 1.
T Data. Address of the currently open location.
X,Y Data. Hold start address and length of PDP-8 data
defined within currently used line in A8 file.
1,2 Data. Temporary use for assembling numeric arguments and
passing data to/from subroutines.
7 Data. Holds last character typed for parser.
[end]