OS-9

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Looking for CoCo help? If you are trying to do something with your old Color Computer, read this quick reference. Want to contribute to this wiki? Be sure to read this first. This CoCo wiki project was started on October 29, 2004. --OS-9 Al

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This page was last updated on 11/29/2013. Total Pages: 744. Total Files: 994.

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Home / Programming - OS-9

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Programming the 6809 using OS-9

OS9 Assembly Language

The OS9 Level I Assembler

The actual machine instructions executed by a computer are sequences of binary numbers that are difficult and inconvenient for people to deal with directly. Creating a machine language program of any length ny hand is tedious, error prone, and time consuming, making it an almost impossible task. Assembly language bridges the gap between computers and people who must write machine-language programs. In assembly language, descriptive mnemonics (abbreviations) for each machine instruction are used which are much easier to learn, read, and remember, are used instead of numerical codes. The assembler also lets the programmer assign sybolic names to memory addresses and constant values. The assembler also has many other features to make assembly language programming easier

This assembler was designed expressly for the modular, multi-tasking enviroment of the OS-9 Operating System, and incorporates built-in functions for calling OS-9, generating memory modules, encouraging the creation of position-independant code, and maintaining seperate program and data sections. It has also been optimized for the use by OS-9 high-level language compilers such as Pascal and C, and can be used on either OS-9 Level 1 or OS-9 Level 2 systems.

Another noteworthy characteristic of this assembler is it's extremely fast assembly speed which is attributable to it's tree-structured symbol table organization. The tree structure dramatically reduces symbol table searching, which is the most time consuming operation performed bay an assembler

The OS-9 Level Two Relocatable Macro Assembler

RMA is a full-featured relocatable macro assembler and linkage editor designed to be used by advanced programmers or with compiler systems.

RMA lets you assemble sections of assembly-language programs independently to create relocatable object files. The linkage editor, RLINK, takes any number of program sections and/or library sections, and combines them into a single OS-9 memory module RMA's features include:

• OS-9 modular, multi-tasking environment support
• Built-in functions for calling OS-9 system routines
• Position-independent, re-entrant code support
• Creating of standard subroutine libraries by allowing programs to be written and assembled separately and then linked together.
• Macro capabilities
• OS-9 Level Two compatibility
• Automatic resolution of global data and program references
• Conditional assembly and library source file support

OS-9 Pascal

About 0S-9 PASCAL

From the OS-9 Pascal Manual

The internal operation of a language as powerful as Pascal must be relatively complex, and running Pascal programs can be quite demanding of the computer. Therefore, microcomputer versions of Pascal traditionally have been quite limited and much slower than their big computer cousins. The gap has been narrowed considerably in 0S-9 Pascal because of two factors. The first factor is the 6809 microprocessor, which was specifically designed to efficiently execute high-level languages such as Pascal. The second factor is the part of 0S-9 Pascal called "PascalS", which allows the Pascal system to utilize disk space as "virtual memory". Being able to utilize disk space as "virtual memory" means that you can run Pascal programs that are much larger than the actual memory size. Indeed, a Pascal compiler as complete as the 0S-9 Pascal compiler would otherwise be too big to fit in your computer's memory.

One other unusual characteristic of 0S-9 Pascal is its ability to compile and run programs in either "P-code" or "native code" forms. "P-codes" are instructions particularly created for an ideal , imaginary "Pascal Computer". The 6809 can't directly execute P-code instructions, so a program called a "P-code interpreter" is used to simulate the ideal "Pascal Computer". Most microcomputer versions of Pascal use the P-code concept because it simplifies the design of the compiler and makes most effic1ient use of a limited amount of memory. Another plus for P-code is that while programs are running, the P-code interpreter can perform thorough error checks and can give excellent diagnostic messages.

Using P-code, the execution speed of programs is relatively slow compared to true machine language. Each P-code instruction causes actual machine language instructions to be run in the interpreter program (which are "overhead" and not actually needed to carry out the original Pascal program). 0S-9 Pascal provides a unique solution to this problem by means of a program called a "native code translator". The native code translator takes a P-code program and translates it to 6809 assembly language (machine language) source code. Both the P-code and the native code forms of the program work exactly the same way - except that the native code version will run from four to ten times faster! And because the output of the translator is a text file that is processed by the standard 0S-9 assembler, you can examine or manually edit it if you wish.

Why even bother with P-code? One reason is that very big programs will only fit in your computer in P-code form. While Pcode is not as fast as native code, in many cases speed is not an important enough factor to bother with the optional translation step. Perhaps the main value of P-code is its use in program debugging because the P-code interpreter has more comprehensive error checking and diagnostics. Typically, 0S-9 Pascal users debug programs in p-code form and translate to native code as a final step.

OS-9 "C" Programming Language

Introduction

From The C Compiler's User Manual

C was originally developed at the Bel Telephone Laboratories as an implementation language for the UNIX operating system by Brian Kernighan and Dennis Ritchie. They also wrote a book titled The C Programming Language which is universally accepted as the standard for the language. It is an interesting reflection on the language that although no formal industry-wide "standard" was ever developed for C, programs written in C tend to be far more portable between radically different computer systems as compared to so-called "standardized" languages such as BASIC, COBOL, and PASCAL. The reason C is so portable is that the language is so inherently expandable that if some special function is required, the user can create a portable extension to the language, as opposed to the common practice of adding additional statements to the language. For example, the number of special-purpose BASIC dialects defies all reason. A lesser factor is the underlying UNIX operating system, which is also sufficiently versatile to discourage nonstandardization of the language. Indeed, standard C compilers and UNIX are intimately related. Fortunately, the 6809 microprocessor, the OS-9 operating system, and the C language form an outstanding combination. The 6809 was specifically designed to efficiently run high-level languages, and its stack-oriented instruction set and versatile repertoire of addressing modes handle the C language very well. As mentioned previously, UNIX and C are closely related, and because OS-9 is derived from UNIX, it also supports C to the degree that almost any application written in C can be transported from a UNIX system to an OS-9 system, recompiled, and corrected executed.

The Language Implementation

OS-9 C is implemented almost exactly as described in The C Programming Language by Kernighan and Ritchie (hereafter referred to as K&R). A copy of this book, which serves as the language reference manual, is included with each software package. Although this version of C follows the specification faithfully, there are some differences. The differences mostly reflect parts of C that are obsolete or the constraints imposed by memory size limitations.

Differences From the K&R Specification

• Bit fields are not supported.
• Constant expressions for initializers may include arithmetic operators only if all the operands are of type int or char.
• The older forms of assignment operators, =+ or =*, which are recognized by some C compilers, are not supported. You must use the newer forms, +=, *=, etc.
• "#ifdef (#ifndef) ... [#else...] #endif" is supported but "#if <constant expression>" is not.
• It is not possible to extend macro definitions or strings over more than one line of source code.
• The escape sequence for newline '\n' refers to the ASCII carriage return character (used by OS-9 for end-of-line), not linefeed (hex 0A). Programs which use '\n' for end-of-line (which includes all programs in K&R) will still work properly.

Enhancements and Extensions

The "Direct" Storage Class

The 6809 microprocessor instruction for accessing memory via an index register or the stack pointer can be relatively short and fast when they are used in C programs to access "auto" (function local) variables or function arguments. The instructions for accessing global variables are normally not so nice and must be four-bytes long and correspondingly slow. However, the 6809 has a nice feature which helps considerably. Memory, anywhere in a single page (256 byte block), may be accessed with fast, two byte instructions. This is called the "direct page", and at any time its location is specified by the contents of the "direct page register" within the processor. The linkage editor sorts out where this should be, and it need not concern the program, who only needs to specify for the compiler which variables should be in the direct page to give the maximum benefit in code size and execution speed. To this end, a new storage class specifier is recognized by the compiler. In the manner of K&R page 192, the sc-specifier list is extended as follows:

Sc-specifier:

• auto
• static
• extern
• register
• typedef
• direct (extension)
• extern direct (extension)
• static direct (extension)

The new keyword may be used in place of one of the other sc-specifiers, and its effect is that the variable will be placed in the direct page. direct creates a global direct page variable. extern direct references an external-type direct page variable and static direct creates a local direct page variable. These new classes may not be used to declare function arguments. "Direct" variables can be initialized but will, as with other variables not explicitly initialized, have the value zero at the start of program execution. 255 bytes are available in the direct page (the linker requires one byte). If all the direct variables occupy less than the full 255 bytes, the remaining global variables will occupy the balance and memory above if necessary. If too many bytes of storage are requested in the direct page, the linkage editor will report an error, and the programmer will have to reduce the use of direct variables to fit the 256 bytes addressable by the 6809.

It should be kept in mind that direct is unique to this compiler, and it may not be possible to transport programs written using direct to other environments without modification.

Embedded Assembly Language

As versatile as C is, occasionally there are some things that can only be done (or done at maximum speed) in assembly language. The OS-9 C compiler permits user-supplied assembly-language statements to be directly embedded in C source programs.

OS-9 Basic09

From the Basic09 manual: Basic09 is an enhanced structured BASIC language programming system specially created for the 6809 Advanced Microprocessor. In addition to the standard BASIC language statements and functions, Basic09 includes many of the most useful elements of the Pascal programming language so that programs can be modular, well-structured, and use sophisticated data structures. It also permits full access to almost all of the OS-9 Operating System commands and functions so it can be used as a systems programming language. These features make Basic09 an ideal language for many applications: scientific, business, industrial control, education and more.

Basic09 is unusual in that it is an Interactive Compiler that has the best of both kinds of language system: it gives the fast execution speed typical of compiler languages plus the ease of use and memory space efficiency typical of interpreter languages. Basic09 is truly a complete programming system that includes a powerful text editor, multi-pass compiler, run-time interpreter, high-level interactive debugger, and a system executive. Each of these components was carefully integrated so the user "sees" a friendly, highly interactive programming resource that provides all the tools and helpful "extra" facilities needed for fast, accurate creation and testing of structured programs.

• The Structure of I-Code

Basic09 Comparisons

                       Basic09       RunB          GFX        GFX2        Inkey    SysCall
                       ============  ============  =========  ==========  =======  =======
OS-9 Dragon Level 1    5AB5 (23221)  <do not have any of these from the Dragon version>
OS-9 Level 1           5ACC (23244)  2F99 (12185)  1F5 (501)  <N/A>       5E (94)  <N/A>
OS-9 Level 2           5ACC (23244)  2F99 (12185)  1F5 (501)  8CA (2250)  5F (95)  63 (99)
NitrOS-9 Level 1       5A29 (23081)  2FA7 (12199)  1F5 (501)  <N/A>       5F (95)  63 (99)
NitrOS-9 Level 2 6809  5A29 (23081)  2FA7 (12199)  1F5 (501)  8CA (2250)  5F (95)  63 (99)
NitrOS-9 Level 2 6309  5955 (22869)  2FA7 (12199)  1F5 (501)  8CA (2250)  5F (95)  63 (99)
                       ============  ============  =========  ==========  =======  =======

         (Dragon)                                                 (6809)        (6309)
        OS9 Level 1   OS9 Level 1   NOS9 Level 1  OS9 Level 2   NOS9 Level 2  NOS9 Level 2
        ============  ============  ============  ============  ============  ============
Basic09 5AB5 (23221)  5ACC (23244)  5A29 (23081)  5ACC (23244)  5A29 (23081)  5955 (22869)
RunB    ???           2F99 (12185)  2FA7 (12199)  2F99 (12185)  2FA7 (12199)  2FA7 (12199)
GFX     ???            1F5 (501)     1F5 (501)     1F5 (501)     1F5 (501)     1F5 (501)  
GFX2    ???           <N/A>         <N/A>          8CA (2250)    8CA (2250)    8CA (2250)  
Inkey   ???             5E (94)       5F (95)       5F (95)       5F (95)       5F (95)
SysCall ???           <N/A>           63 (99)       63 (99)       63 (99)       63 (99)
        ============  ============  ============  ============  ============  ============

Comparisons are between OS-9 Level 1 and OS-9 Level 2 versions.
All values in hex
in case I have it backwards:
MSB LSB
 10 00
 20 00

BASIC09:
=======
The difference between Level 1 and Level 2 Basic09 is a 4K data buffer. Level 1
Basic09 has a default workspace size of 4K, and Level 2 has a default workspace
size of 8K. Module differences include the MSB of the module header Runtime
Variable Storage Size field, the revision number bump to 1, and the module CRC.

RUNB:
====
The Level 1 and Level 2 RunB has the same differences as Basic09.

SYSCALL:
=======
Level 1 did not include SysCall, and if it had, it would have been named with
all caps (SYSCALL), as all of the modules on the disk are in all caps, including
Basic09.

INKEY:
=====
The Level 1 Inkey subroutine has 4 bytes that are different from, plus the CRC,
and is 1 byte smaller than the Level 2 version (name reference includes the hi-
bit set last character):

Header differences:

Module Size changed from 005E to 005F
Module Attributes/Revision changed from 81 to 80
1st field after Header Parity changed from 0012 to 0013
The Edition byte (the first byte after the module name) is a value of 01, and it
is the reason the Level 2 version is 1 byte longer than the Level 1 version. It
was inserted here in the level 2 version of Inkey.

The CRC values differ:
1A6916 as compared to FE0637

GFX:
===
According to the module header definition, the 8th and 9th bytes are the
Attributes/Revision byte and the Header Parity byte. They are changed from 81
and EC in the Level 1 version to 80 and ED in the Level 2 version.

The CRC values differ:
DDC98B as compared to C29373

This concludes the immediate comparisons of the Level 1 and Level 2 versions of
Basic09. Other than the differences stated above, both versions are identical.
SysCall was not included on the Level 1 Basic09 diskette as sold by Radio
Shack/Tandy. It is my understanding that a assembly source listing for SysCall
exists somewhere in the OS-9 manuals. I will modify this document when I have
that listing.

CoCo OS-9 Level 1 Basic09 comparison to Dragon OS-9 Level 1 Basic09:
(CoCo value is listed first)

header differences:

Module Size is changed from 5ACC to 5AB5
Module Header Parity changed from A8 to D1
1st int after Header Parity changed from 07C1 to 07AA
3rd int after Header Parity changed from 00DC to 00C5
4th int after Header Parity changed from 1CA5 to 1C8E
5th int after Header Parity changed from 255A to 2543
6th int after Header Parity changed from 31E8 to 31D1
7th int after Header Parity changed from 3C09 to 3BF2
8th int after Header Parity changed from 5084 to 506D

0039-52    RS VERSION 01.00.00. removed from Dragon version
00B7-C1 TANDY CORP changed at 009B-A9 to DRAGON DATA LTD

0822 DD changed at 080B to F4
082D DF changed at 0816 to F6
08A9 7A changed at 0892 to 91
08AF 6B changed at 0898 to 82

CRC value at 5AC9 C5054F changed at 5AB2 to E3C48D

This concludes the CoCo and Dragon version comparisons. I do not understand the
differences in the code as yet.

SysCall comparisons between OS-9 Level 2 and NOS-9 Level 1 and Level 2
===================
The NitrOS-9 Level 1 and Level 2 versions of SysCall are identical. The OS-9
Level 2 version has differences from the NitrOS-9 versions, as follows:

Attributes/Revision byte 81 changed to 80
Header Parity byte 7B changed to 7A
CRC F37B74 changed to 8583E2

Source Listings

Inkey Level 1

Inkey listing from Basic09 Level 1 Programming manual Revision F February 1983
Appendix A: Sample Programs: pp.107-108 (spacing between fields added by me)

***************
* INKEY - a subroutine for BASIC09 by Robert Doggett
* Called by: RUN INKEY(StrVar)
*            RUN INKEY(Path, StrVar)
* Inkey determines if a key has been typed on the given path
* (Standard Input if not specified), and if so, returns the next
* character in the String Variable. If no key has been type, the
* null string is returned. If a path is specified, it must be
* either type BYTE or INTEGER.
  0021              TYPE set SBRTN+OBJCT
  0081              REVS set REENT+1
* The Level 2 listing uses SIZE instead of 0
  0000 87CD005E          mod InKeyEnd,InKeyNam,TYPE,REVS,InKeyEnt,0
  000D 496E6B65 InKeyNam fcs "Inkey"
D 0000                   org 0          Parameters
D 0000            Return rmb 2          Return addr of caller
D 0002            PCount rmb 2          Num of params following
D 0004            Param1 rmb 2          1st param addr
D 0006           Length1 rmb 2          size
D 0008            Param2 rmb 2          2nd param addr
D 000A           Length2 rmb 2          size
  0012 3064     InKeyEnt leax Param1,S
  0014 EC62              ldd PCount,S   Get parameter count
  0016 10830001          cmpd #1         just one parameter?
* this line in the Level 2 listing shows 2727
  001A 2717              beq InKey20    ..Yes; default path A=0
  001C 10830002          cmpd #2         Are there two params?
  0020 2635              bne ParamErr   No, abort
  0022 ECF804            ldd [Param1,S] Get path number
  0025 AE66              ldx Length1,S
  0027 301F              leax -1,X byte  available?
  0029 2706              beq InKey10    ..Yes; (A)=Path number
  002B 301F              leax -1,X       Integer?
  002D 2628              bne ParamErr   ..No; abort
  002F 1F98              tfr B,A
  0031 3068      InKey10 leax Param2,S
  0033 EE02      InKey20 ldu 2,X        length of string
  0035 AE84              ldx 0,X        addr of string
  0037 C6FF              ldb #$FF
  0039 E784              stb 0,X        Initialize to null str
  003B 11830002          cmpu #2         at least two-byte str?
  003F 2502              blo InKey30    ..No
  0041 E701              stb 1,X        put str terminator
  0043 C601      InKey30 ldb #SS.Ready
  0045 103F8D            OS9 I$GetStt   is there an data ready?
  0048 2508              bcs InKey90    ..No; exit
  004A 108E0001          ldy #1
  004E 103F89            OS9 I$Read     Read one byte
  0051 39                rts
  0052 C1F6      InKey90 cmpb #E$NotRdy
  0054 2603              bne InKeyErr
  0056 39                rts            (carry clear)
  0057 C638     ParamErr ldb #E$Param   Parameter Error
  0059 43       InKeyErr coma
  005A 39                rts
  005B 1A6926            emod
  005E          InKeyEnd equ *

Inkey Level 2

Inkey listing from Level 2 Basic09 Reference
Appendix B: The Inkey Program: pp.B-1,B-2

This listing has differences from the listing in the Level 1 manual.

***************
* INKEY - a subroutine for BASIC09 by Robert Doggett
* Called by: RUN INKEY(StrVar)
*            RUN INKEY(Path, StrVar)
* Inkey determines if a key has been typed on the given path
* (Standard Input if not specified), and if so, returns the next
* character in the String Variable. If no key has been type, the
* null string is returned. If a path is specified, it must be
* either type BYTE or INTEGER.
***********************************
* These lines do not exist in the Level 1 listing
                         NAM INKEY
                         IFP1
                         USE /D0/DEFS/OS9DEFS
                         ENDC
***********************************
  0021              TYPE set SBRTN+OBJCT
  0081              REVS set REENT+1
* The Level 1 listing uses 0 instead of SIZE
  0000 87CD005E          mod InKeyEnd,InKeyNam,TYPE,REVS,InKeyEnt,SIZE
  000D 496E6B65 InKeyNam fcs "Inkey"
D 0000                   org 0          Parameters
D 0000            Return rmb 2          Return addr of caller
D 0002            PCount rmb 2          Num of params following
D 0004            Param1 rmb 2          1st param addr
D 0006           Length1 rmb 2          size
D 0008            Param2 rmb 2          2nd param addr
D 000A           Length2 rmb 2          size
***********************************
* These lines do not exist in the Level 1 listing
  000C           E$Param equ $38
  000E              SIZE equ *
***********************************
  0012 3064     InKeyEnt leax Param1,S
  0014 EC62              ldd PCount,S   Get parameter count
  0016 10830001          cmpd #1        just one parameter?
* this line in the Level 1 listing shows 2717
  001A 2727              beq InKey20    ..Yes; default path A=0
  001C 10830002          cmpd #2        Are there two params?
  0020 2635              bne ParamErr   No, abort
  0022 ECF804            ldd [Param1,S] Get path number
  0025 AE66              ldx Length1,S
  0027 301F              leax -1,X byte available?
  0029 2706              beq InKey10    ..Yes; (A)=Path number
  002B 301F              leax -1,X      Integer?
  002D 2628              bne ParamErr   ..No; abort
  002F 1F98              tfr B,A
  0031 3068      InKey10 leax Param2,S
  0033 EE02      InKey20 ldu 2,X        length of string
  0035 AE84              ldx 0,X        addr of string
  0037 C6FF              ldb #$FF
  0039 E784              stb 0,X        Initialize to null str
  003B 11830002          cmpu #2        at least two-byte str?
  003F 2502              blo InKey30    ..No
  0041 E701              stb 1,X        put str terminator
  0043 C601      InKey30 ldb #SS.Ready
  0045 103F8D            OS9 I$GetStt   is there an data ready?
  0048 2508              bcs InKey90    ..No; exit
  004A 108E0001          ldy #1
  004E 103F89            OS9 I$Read     Read one byte
  0051 39                rts
  0052 C1F6      InKey90 cmpb #E$NotRdy
  0054 2603              bne InKeyErr
  0056 39                rts            (carry clear)
  0057 C638     ParamErr ldb #E$Param   Parameter Error
  0059 43       InKeyErr coma
  005A 39                rts
  005B 1A6926            emod
  005E          InKeyEnd equ *

SysCall Level 1

SysCall Listing
November 1984, Volume 4, Number 4 of The Rainbow Magazine
Page 281, under the segment title "Microware's Third Annual OS-9 Users Seminar"
Mid-page, center column, there is a call-out that says:

"SysCall ... lets you program OS-9 system calls directly in your BASIC09 program."

Lower-right corner of the page, the last part of the 3rd column:

Two Useful Routines

We're printing two useful routines this month. SysCall is an assembly language subroutine designed to work
with BASIC09. It lets you program OS-9 system calls directly in your BASIC09 program. One of the handiest
tools you'll ever find, it was written by Robert Doggett at Microware.

Also, we are presenting three BASIC09 procedures that show you how to create and use pipes. The procedure
"POpen" creates a pipe by DUPEing one of the standard paths and using it as the path for the pipe that will
go to or from the FORKed pipeline process. It uses SysCall.

The procedure "OutPipe" calls POpen to create a pipe to a spooler. The pipe lets the output of OutPipe be
read and printed by the spooler. If you do not have a spooler program, you can open a path to any other
program by changing the parameters in the RUN statement.

The procedure "InPipe" calls POpen to create a pipe from the OS-9 MDIR utility command to itself. InPipe can
then read the standard output path from MDIR and display its output.

Special thanks to Bill Pierce for finding this jewel and bringing it to this collection. The listing below
appears exactly as it appears in the Rainbow's article on page 284. The extra comments between lines 00007 and 00007 are mine. I made a correction to the procedure listing for filesize.

THE PROCEDURE SYSCALL
Microware OS-9 Assembler 2.1 09/05/84 22:32:33                       Page 001
- OS·9 System Symbol Definitions
--------------- cut here ---------------
00001        ***************************************
00002        * SYSCALL - a powerful subroutine for use with Basic09
00003        * A special thanks to Robert Doggett for writing this routine.
00004        
00005        * Basic09 calling suquence:
00006        * TYPE Registers=CC,A,B,DP:BYTE; X,Y,U:INTEGER
00007        * DIM regs:Registers
             *
             * There is no DIM statement for code, which must be a BYTE or INTEGER value,
             * and a non-DIM'd variable in Basic09 is either a type REAL or, with a $ as the
             * last character of the name, a 32-character STRING.
             * DIM code:BYTE
             *
00008        * RUN SysCall(code,registers)
00009        
00010        * SysCall will allow you to execute ANY OS-9 System call from
00011        * your Basic09 programs. BE WARNED!!! SysCall can be VERY
00012        * dangerous, since it permits you to do things you may not want
00013        * done during program execution (like format disks, write
00014        * thousands of bytea all at once, and so on). However, it can
00015        * also be very useful, IF you know what you are doing.
00016        
00017        * NOTE: This version of SysCall will cause a Basic09 runtime
00018        * error to occur if your system call returns an error. This can
00019        * be easily overcome, as noted below. If you do this, you
00020        * must check "regs.CC" to see if a system error has occurred.
00021        
00022        * Here is an example of one possible use you may have for SysCall
00023        *
00024        * PROCEDURE filesize
00025        * TYPE Registers=CC,A,B,DP:BYTE; X,Y,U:INTEGER
00026        * DIM regs:Registers
00027        * DIM path,callcode:BYTE \(* or INTEGER *)
00028        * OPEN #path,"test":READ
00029        * regs.A:=path
00030        * regs.B:=2 \(* I$GetStt code *)
00031        * RUN SysCall(callcode,regs)
00032        * CLOSE #path
00033        * PRINT USING "filesize = 0',2(h4)",regs.X; regs.U
00034        
00035                           USE  /d0/defs/os9defs
00421                           opt  1
00422        
00423        
00424   0021          TYPE      set  SBRTN+ONJCT
00425   0081          REVS      set  REENT+1
00426   0000 87CD005E           mod  SyCalEnd,SyCalNam,TYPE,REVS,SyCalEnt,0
00427   000D 53797343 SyCalNam  fcs  "SysCall"
00428   0014 02                 fcb  2          edition number
00429        
00430   0038          E$Paras   equ  56         Basic09's parameter error code
00431   103F          M.OS9     equ  $103F      OS-9 system call machine code
00432   0039          M.RTS     equ  $39        rts machine code
00433        
00434 D 0000                    org  0          stacked variable
00435 D 0000          Return    rmb  2          Return address
00436 D 0002          PCount    rmb  2          number of params passed
00437 D 0004          Function  rmb  4          OS-9 function code
00438 D 0008          Regs      rmb  4          Register image
00439        
00440   0015 EC62     SyCalEnt  ldd  PCount,s   Get parameter count
00441   0017 10830002           cmpd #2         exactly 2 parameters?
00442   001B 263A               bne  ParamErr   abort if not
00443   001D EC6A               ldd  Regs+2,s   check size of register image
00444   001F 1083000A           cmpd #10        exactly 10 bytes?
00445   0023 2632               bne  ParamErr   abort if not
--------------- cut here ---------------
Microware OS-9 Assembler 2.1 09/05/84 22:32:33                       Page 002
- OS·9 System Symbol Definitions
--------------- cut here ---------------
00446   0025 ECF804             ldd  [Function,S] get os-9 function code
00447   0028 AE66               ldx  Function+2,S get size of function param
00448   002A 301F               leax -1,X        INTEGER?
00449   002C 2629               bne  ParamErr    abort if not
00450   002E 1F98               tfr  B,A
00451        
00452        * Now you build your OS9 call and return from subroutine on
00453        * stack (A)=OS9 function call
00454        
00455   0030 C639     SysCall   ldb  #M.RTS      get "rts" machine code
00456   0032 3406               pshs D
00457   0034 CC103F             ldd  #M.OS9      get OS-9 machine code
00458   0037 3406               pshs D
00459   0039 EE6C               ldu  Regs+4,S    get register image ptr
00460   003B EC41               ldd  R$D,U       initialize regs for system call
00461   003D AE44               ldx  R$X,U
00462   003F 10AE46             ldy  R$Y,U
00463   0042 EE48               ldu  R$U,U
00464   0044 ADE4               jsr  0,S         execute system call
00465   0046 3441               pshs CC,U        save CC,U
00466   0048 EE6F               ldu  Regs+7,S
00467   004A 3348               leau R$U,U
00468   004C 363E               pshu A,B,DP,X,Y  return unpdatd regs to caller
00469   004E 3512               puls A,X         get CC,U
00470   0050 A7C2               sta  ,-U
00471   0052 AF48               stx  R$U,U
00472   0054 3264               leas 4,S         discard OS-9 call subroutine
00473        
00474        * If you want to eliminate the possibility of a runtime error
00475        * remove the comment designator (*) from the next line
00476        
00477        * clrb
00478   0056 39                 rts
00479   0057 53        ParamErr comb             return carry set
00480   0058 C638               ldb  #E$Param    Parameter error
00481   005A 39                 rts
00482        
00483   005B B931F4             emod
00484   005E           SyCalEnd equ  *

00000 error(s)
00000 warning(s)
$005E 00094 program bytes generated
$00E5 00229 data bytes allocated
$1006 04102 bytes used for symbols