X-Git-Url: http://gitweb.hachti.de/?a=blobdiff_plain;ds=sidebyside;f=sw%2Fkermit%2Fk12%2Fk12ipl.doc;fp=sw%2Fkermit%2Fk12%2Fk12ipl.doc;h=b2500f989f00fd9bdec20b7b86071583285e2635;hb=81e70d488b71bf995c459ca3a02c025993460ffa;hp=0000000000000000000000000000000000000000;hpb=07ec0278333ed187ac242dedcff13c56cf1b0b91;p=pdp8.git diff --git a/sw/kermit/k12/k12ipl.doc b/sw/kermit/k12/k12ipl.doc new file mode 100644 index 0000000..b2500f9 --- /dev/null +++ b/sw/kermit/k12/k12ipl.doc @@ -0,0 +1,66 @@ +From: Charles Lasner +Subject: Initial Program Load (.IPL) format description + + Some of the latest KERMIT-12 binary files are encoded in a +specialized format designed to allow direct memory loading without an +elaborate protocol such as KERMIT. This document will describe the +internal encoding of this format known as IPL, and related subjects. + + The Initial Program Load (.IPL) format is designed expressly for +use with the IPL loading program. An error-free connection to a +serving host is required as no checking or recovery is performed by +the program. (The program itself is meant to be keyed in on the +target PDP-8 where there is no other means of acquiring KERMIT-12.) +The format is also meant to be "printable" in the same sense as +ENCODE, .BOO, or uuencode files. This makes the file format more +"friendly" to the host system, and allows simple editing of the file +to insert comments, etc. + + An .IPL file starts with at least one lower-case character (not +counting `) meaning any character in the range 141-177 octal. Any number +of similar characters may follow immediately to create an arbitrary length +leader, but the lower-case requirement must be strictly enforced. Once a +non-lower-case character is encountered, it is accepted as the first data +character. Data characters continue throughout the rest of the file until +the next occurrence of a lower-case character which ends the loading. Any +characters past this point are ignored and can be freely added as a +trailing comment. + + Throughout the entire .IPL file, control characters and +(000-040 octal) are ignored and may be used within the leader to make +the file comment(s) more readable. In some loading situations, +or characters may be pre-pended to the file to give the +operator sufficient time to run down the hall between machines in +different rooms to start the PDP-8 loading program after first +starting the server. Data lines are broken every 64 characters with +/ to make the file more "readable" to the host system. + + Each data character in the body of the file represents six bits of +PDP-8 data encoded in the form (value+041 octal). This causes 00 octal to +be represented as ! through 77 octal to be represented as `. Data +characters are taken in pairs where the first character is the upper six +bits and the second is the lower six bits of a twelve bit word. Loading is +implied to start at 0000 of the loading field and continues through at most +7577. The operating system generally prohibits loading into 7600-7777. +This is not a problem since KERMIT-12 conforms to these limitations as a +matter of design. If the loading field is 3 or greater (or possibly 2 in +certain configurations) then the entire field can possibly be loaded. This +is never recommended because such a file would violate loading restrictions +of certain configurations. (The general rule is to never load into +x7600-x7777 for any field x in the range 0-7.) + + The loading field itself is not contained in the file data, so it is +the user's responsibility to setup the loading program parameters +accordingly. File comments (in lower-case if in the leader) often contain +this information to aid the user. After loading is complete, the loading +program exits to the operating system. The user must save the recently +loaded data as an image (.SV) file by providing explicit arguments to a +SAVE command. It is recommended that the appropriate command be contained +in the trailer of the .IPL file as a comment. Placement at the end of the +file allows the commentary to be in upper-case, thus allowing it to be +given in the exact form required by OS/8. Certain characters such as "." +are required in the complete documentation of these commands which are not +allowed in the leader area. The leader can contain a comment referring the +user to the end of the file for the information itself. + +[end of file]