NEC CP/M-86 User manual

~~ Advanced
Ar-L Personal Computer
TM
CP/M-86 System Reference Guide
NEe
NEe Information Svstems,lnc.
819-000102-2001 REV. 01
8-83

Important Notice
(1) All rights reserved. This manual is protected by copyright. No part of this manual may be
reproduced in any form whatsoever without the written permission
of the copyright owner.
(2) The policy
of NEe being that of continuous product improvement, the contents of this manual
are subject
to change, from time to time, without notice.
(3) All efforts have been made to ensure that the contents
of this manual are correct; however, should
any errors be detected, NEC would greatly appreciate being informed.
(4) NEC can assume no responsibility for errors in this manual
or their consequences.
©Copyright
1983 by NEC Corporation.

Contents
Page
PREFACE........................................................ lX
Chapter 1 CP/M-86 System Overview
CP/M-86 GENERAL CHARACTERISTICS. .
.. . .. . . . . . . . .. . . . . . . .... 1-1
CP/M-80 AND CP/M-86 DIFFERENCES............................ 1-4
Relocatable Groups. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1-4
Memory Models. ... . . .. . . . . .. . . ... . . . . .. . .. . . . . . .. ... . . . . . .... 1-4
Disk Definition Tables ......................................... 1-5
Bootstrap Operation ...... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5
BDOS Calls. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1-5
Addressing ................................................... 1-5
Program Termination. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . .. 1-6
Chapter 2 Command Setup and Execution Under CP/M -86
CCP BUILT-IN AND TRANSIENT COMMANDS.................... 2-1
TRANSIENT PROGRAM EXECUTION MODELS ................... 2-2
The 8080 Memory Model. . . . . . .. .... . . . .. . .. . . . . . . . ... . . . . . . ... 2-3
The Small Memory Model ...................................... 2-5
The Compact Memory Model ................................... 2-6
Base Page Initialization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.. 2- 7
TRANSIENT PROGRAM
LOAD. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2-9
TRANSIENT PROGRAM EXIT. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2-9
Chapter 3 Command (CMD) File Generation
INTEL 8086 HEX
FILE FORMAT.................................. 3-1
OPERATION OF GENCMD ....................................... 3-3
COMMAND FILE FORMAT ....................................... 3-6
iii

iv
Contents (cont' d)
Page
Chapter 4 Basic Disk Operating System (BDOS) Functions
BDOS PARAMETERS............................................. 4-1
BDOS FUNCTION CODES ........ : . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 4-2
Simple BDOS Calls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 4-4
BDOS File Operations ......................................... 4-10
BDOS Memory Management and Program Functions. . . . . . . . . . . . . .. 4-32
Chapter 5 Basic 1/0 System (BIOS) Organization
ORGANIZATION OF THE BIOS................................... 5-2
THE BIOS JUMP VECTOR. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5-3
BIOS SUBROUTINES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5-3
STANDARD BIOS SUBROUTINE ENTRY POINTS.................. 5-5
System Initialization Subroutines ................................ 5-5
Simple Character 1/0 Subroutines. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5-6
10BYTE Function. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5-8
Disk 1/0 Subroutines .......................................... 5-10
Other Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.. 5-18
Chapter 6 Advanced BIOS Functions
CRT ESCAPE SEQUENCE FUNCTIONS............................ 6-1
Format and Definitions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 6-1
APC Escape Code Sequences. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 6-4
ASCII CONTROL
CODES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 6-9
EXTENDED FUNCTION CALLS .................................. 6-9
Get Time
and Date ............................................ 6-10
Set Time and Date. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 6-11
Play Music .................................................... 6-11
Sound Beep. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 6-15
Report Cursor Position. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 6-17
Auto Power Off ............................................... 6-17
Initialize Keyboard
FIFO Buffer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 6-18
Direct CRT 1/0 ............................................... 6-18
Write CMOS
.................................................. 6-26
Read CMOS
.................................................. 6-26
Initialize
RS 232C ............................................. 6-27

Contents (cont' d)
Page
Chapter 7 Disk Definition Tables
DISK PARAMETER TABLE FORMAT ............................. 7-1
DISK DEFINITION TABLES ...................................... 7-7
PHYSICAL AND LOGICAL STRUCTURES
FOR FLOPPY DISKETTES ........................................ 7-11
Chapter 8 CP /M-86 Bootstrap and Adaptation Procedures
THE COLD START LOAD OPERATION.. .... . . .. .. . . .. .. .. . .. .. .. 8-2
ORGANIZATION OF CPM.SYS. . ... . . . . . . . . . . . . . . . . . . .. . . . . . . . . . .. 8-4
Chapter 9 GSX-86: Graphics for the APC
WHAT IS GSX-86................................................. 9-1
GSX-86 and Application Programs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 9-1
GSX-86 and Graphics Products... . . . . . . .. . . . . . . . . . . . . .. . . . . . . . .. 9-2
USING GSX-86 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 9-2
Setting Up GSX-86 ............................................ 9-2
Updating the Assignment Table. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 9-3
Device Drivers ............. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 9-4
Invoking GSX-86 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.. 9-6
Warm Starts and Cold Starts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 9-6
OVERVIEW OF GRAPHICS SYSTEM EXTENSION STRUCTURE .... 9-6
GSX-86 Architecture. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.. 9-6
Memory Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 9-7
THE GRAPHICS DEVICE OPERATING SYSTEM (GDOS) ........... 9-8
Virtual Device Interface (VDI). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 9-9
Normalized Device Coordinates ................................. 9-10
GDOS Opcodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.. 9-11
THE GRAPHICS INPUT/OUTPUT SYSTEM (GIOS) ................. 9-44
Creating a GIOS File
........................................... 9-44
v

vi
Contents (cont' d)
Appendix A Escape Sequences
Appendix B Soft Key Table Memory Format
Appendix C Auxiliary Character Generator RAM Format
Appendix D Memory Map
Appendix E Keyboard Structures
Appendix F CP/M-86 Control Characters
Appendix G CP/M-86 Error Messages
Appendix H CBIOS Error Messages
Appendix I Blocking and Deblocking Algorithms
Appendix J Physical Format
of Hard Disks
Appendix K GSX-86 Device Specific Information

Illustrations
Figure
2-1
2-2
2-3
2-4
3-1
4-1
4-2
4-3
5-1
5-2
6-1
6-2
6-3
6-4
6-5
6-6
8-1
8-2
9-1
C-l
C-2
E-l
E-2
E-3
J-l
J-2
J-3
Title Page
CP/M-86 8080 Memory Model... . . .... . . . . . . . ... . . . . ...... .. 2-4
CP/M-86 Small Memory Model. . ..... . . ... . . . ... .. . ..... .... 2-5
CP/M-86 Compact Memory Model..... .. . . .. . ... . . . . ... .. ... 2-6
CP/M-86 Base Page Values. .. . . . . . . . . . . . . . . . . ... . . . . . . . . . . .. 2-8
CMD File Header Format.. ... . . . ..... .. . ... . ... . . . . ... ..... 3-6
Example Memory Allocation
.......... . . . . . . . . . . . . . . . . . . . . .. 4-33
Example Memory Region
................................... 4-34
Example Memory Regions
................................... 4-34
APC CBIOS Function Calls. . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . .. 5-1
General CP/M-86 Organization. . . . . . . . . . . . . . . . .. . . . . . . . . . . .. 5-2
Escape Code Sequence Example. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 6-3
Display Request
Block. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 6-19
DMA Transfer ............................................ 6-20
Attribute Date Byte Format ................................. 6-22
Roll
Down Screen .......................................... 6-24
Roll
Up Screen ............................................ 6-25
LOADER Organization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 8-3
CPM.SYS File Organization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 8-5
GSX-86 Memory Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 9-8
Sample Bit
Pattern of Graphic Character. . . . . . . . . . . . . . . . . . . . .. C-2
Sample Data in Auxiliary CG RAM .......................... C-2
APC Keyboard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. E-6
APC G RPH 1 Characters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. E-7
APC G RPH2 Characters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. E-8
5Y/' Hard Disk Physical Format (DKM220). . . . . . . . . . . . . . . . . . .. J-2
Error Map. . ... . . . .... . ...... ... . . .. .... .... .. ... . . .. . .... J-4
Error Map and Track Reallocation. . . . . . . . . . . . . .. .. . . . . . . . . .. J-5
vii

Tables
Table Title Page
1-1 CP/M-86 Terms.. . . . . . . . . . ... . . . . . . . ... . . . . . . . . . . . . . . . . . .. 1-3
2-1 CP/M-86 Memory Models. . ...... .. ..... . ...... .... . .. ..... 2-2
3-1 Intel Hex Field Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 3-2
3-2
Group Descriptors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 3-7
4-1 BDOS Parameter Summary..... .... ..... . ....... .. . . . . .. ... 4-1
4-2 CP IM-86 BDOS Functions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 4-3
4-3 Line Editing Controls. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 4-9
4-4 Function 33 (Read Random) Error Codes ..................... 4-25
4-5 Function
34 (Write Random) Error Codes ..................... 4-27
5-1 BIOS Jump Vector. . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . .. 5-4
5-2 CP/M-86 Logical Device Characteristics ...................... 5-6
5-3 IOBYTE Field Definitions .................................. 5-9
6-1 ASCII Control Codes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 6-9
6-2 Extended Function Calls .................................... 6-10
6-3 Melody Data Control Commands ............................ 6-12
6-4 Note Values
............................................... 6-13
6-5 Duration Values ........................................... 6-14
6-6 Short Sound Control Commands. . . . . . . . . . . . . . . . . . . . . . . . . . . .. 6-15
6- 7 Beep Sound Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 6-16
6-8 Direct
CRT 1/0 Function Calls .............................. 6-18
7-1 Disk Parameter Header Elements. . . . . . . . . . . . . . . . . . . . . . . . . . . .. 7-2
7-2 DPH Values for the APC ................................... 7-2
7-3 Disk Parameter Block Fields. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.. 7-4
7-4 BSH and BLM Values for Selected BLS . . . . . . . . . . . . . . . . . . . . . .. 7-5
7-5 Maximum EXM Values. . . . . . . . . . . . . . . . . . . . . . . . . . . •. . . . . . . .. 7-5
7-6 BLS and Number of Directory Entries ........................ 7-6
7-7 DPH Values for the APC ................................... 7-7
7-8 Physical and Logical Addressing for Floppy Diskettes. . . . . . . . . .. 7-8
9-1 Device Drivers Supplied with GSX-86. . . . . . . . . . . . . . . . . . . . . . . .. 9-5
9-2 GDOS Opcodes ........................................... 9-12
E-l Code Table ............................................... E-2
E-2 ASCII Special
Characters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. E-3
E-3 APC Special Characters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.. E-4
E-4 Quick Reference Guide for ASCII Special
Characterl APC Special Character Association. . . . . . . . . . . . . . . .. E-5
viii

Preface
The CPIM-86 Operating System Guide for the APC presents the system program-
ming aspects of CP/M-86, a single-user operating system for the Jl PD8086 16-bit
microprocessor, used by
NEC for the Advanced Personal Computer (APC). The
discussion assumes
that the reader is familiar with CP/M, the Digital Research 8-bit
operating system.
To clarify specific differences with CP/M-86, this document
refers to the 8-bit version
of CP/M as CP/M-80. Elements common to both systems
are simply called
CP/M features.
This Operating System Guide presents an overview
of the CP/M-86 programming
interface conventions.
It also describes procedures for adapting CP /M-86 to a
custom hardware environment.
Chapter 1 gives
an overview of CP/M-86 and summarizes how it differs from
CP/M-80.
Chapter 2 describes the general execution environment while Chapter 3
tells how
to generate command files. Chapter 4 defines theprogramminginterfaces
to the Basic Disk Operating System (BDOS). Chapters 5
and 6 define the standard
and customized features of the Basic Input/ Output System (BIOS). (Chapter 5
includes
CP/M-86 disk operations for both floppy diskette and hard disk media.)
Chapter 7 discusses alteration of the BIOS to support custom disk configurations.
Chapter 8 describes the loading operation and the organization of the CP /M-86
system file. Chapter 9 describes GSX-86, the graphics extension for the APC.
ix

Chapter 1
CP IM-86 System Overview
CP/M-86 GENERAL CHARACTERISTICS
CP/M-86 consists of all the facilities of CP/M-80 with additional features to
account for increased processor address space of up to one megabyte(1,048,576) of
main memory. CP/M-86 maintains file compatibility with all previous versions of
CP/M. It uses the file structure of CP/M Version 2, allowing as many as sixteen
drives
with up tb eight megabytes on each drive. CP/M-80 and CP/M-86 programs
may exchange files without any modification to the file formats.
CP/M-86 resides in the file CPM.SYS, which is loaded into memory by a cold start
loader during system initialization. The cold start loader resides on the first two
tracks of the system disk. CPM.SYS contains three program modules: the Console
Command Processor (CCP), the Basic Disk Operating System (BDOS), and the
Basic
Input/Output System (BIOS). The BIOS distributed on the CP/M system
diskette
has been configured for the APC and is called the Customized BIOS, or
CBIOS. It is made up of three parts: the standard BIOS, the APC escape sequence
functions,
and the extended BIOS. The CCP and BDOS portions occupy approxi-
mately 10K bytes, and the BIOS is approximately 22 bytes. The operating system
executes in
memory above the reserved interrupt locations. The remainder of the
address space may be partitioned into eight non-contiguous regions, as defined in a
BIOStable. Unlike CP/M-80, CP/M-86 does not allow the CCP area to be used as a
data area subsequent to transient program load. All CP/M-86 modules remain in
memory at all times and are not reloaded at a warm start.
Like CP/M-80, CP/M-86 loads and executes memory image files from disk.
Memory image files are preceded by a header record, defined in Chapter 3, which
provides
information required for proper program loading and execution. Memory
image files under CP/M-86 are identified by the CMD file type exte.nsion.
1-1

CP/M-86 System Overview
1-2
Unlike CP/M-80, CP/M-86 does not use absolute locations for system entry or
default variables. The BDOS entry takes place through a reserved software inter-
rupt. Entry to the BIOS is provided by a new BDOS call. Entry to the extended
BIOS is made directlythrough an interruptvector. Two variables maintainedin low
memory under CP/M-80, the default disk number and I/O Byte, are placed in the
CCP and BIOS respectively in CP/M-86. Dependence on absolute addresses is
minimized in CP/M-86 by maintaining inital base page values, such as the default
File
Control Block and default command buffer, in the transient program data
area.
Utilityprograms such as
ED, PIP, STAT, and SUBMIToperate in the same manner
under CP/M-86 and CP/M-80. DDT-86 allows interactive debugging of 8086
machine code. ASM-86 allows assembly language programming and development
for the 8086 using Intel-like mnemonics.
CP/M-86 includes two utilities that replace equivalent CP/M-80 utilities.
• GENCMD (Generate CMD file) replaces the LOAD program ofCP/M-80.
It converts the hexfiles produced by ASM-86 or Intel utilities into memory
image
format suitable for execution under CP/M-86 .
• LDCOPY (Loader Copy) replaces the SYSGEN utility used under
CP/M-80. It is used to copy the cold start loader from a system disk for
replication.
Several terms used throughout this manual are defined in Table 1-1.
A group consists
of segments that are loaded into memory as a single unit. Since a
group may consist of more than 64 bytes, it is the responsibility of the application
program to manage segment registers when accessing code or data beyond the first
64K segment.
CP/M-86 supports eight program groups: the code, data, stack, and extra groups,
and four auxiliary groups. When a code, data, stack, or extra group is loaded,
CP/M-86 sets the respective segment register (CS, DS, SS or ES) to the base of the
group. CP/M-86 can also loadfourauxiliary groups. A transient program manages
the location
of the auxiliary groups using values stored by CP/M-86 in the user's
base page.

CPIM-86System Overview
Table 1-1 CP/M-86 Terms
TERM
MEANING
Nibble
4-bit half-byte
Byte
8-bit value
Word
16-bit value
Double Word
32-bit value
Paragraph
16 contiguous bytes
Paragraph Boundary
An address evenly divisible by 16 (low
order nibble 0)
Segment
Up to 64K contiguous bytes
Segment Register
One of CS, OS, ES, or SS
Offset
16-bit displacement from a segment reg-
ister
Group
A segment-register-rela tive reloca table
program unit
Address
The effective memory address derived
from the combination of a segment reg-
ister value plus an offset value
1-3

CPIM-86System Overview
1-4
CP/M-80 AND CP/M-86 DIFFERENCES
The structure of CP/M-86 is as close to CP/M-80 as possible. This provides a
familiar programming environment which allows application programs to be
transported to the 8086 processor with minimal effort. This section points out
specific differences between CP/M-80 and CP/M-86 to reduce your time in scan-
ningthe manual if you are alreadyfamiliar with CP /M-80. Theterms and concepts
presented in this section are explained in detail throughout the manual, so refer to
the Table of Contents for the relevant chapters which provide specific definitions
and information.
Relocatable Groups
The fundamental difference between
CP/M-80 and CP/M-86 is found in the
management of the various relocatable groups. Although CP/M-80 references
absolute memory locations by necessity,
CP /M-86 takes advantage of the static
relocation inherent in the 8086 processor. The operating system itself is loaded
directly above the interrupt locations, at location 0400H, and relocatable transient
programs load in the bestfit memoryregion. However, you can load CP /M-86 into
any portion of memory without changing the operating system (thus, there is no
MOVCPM utility with CP /M-86), and transient programs will load and run in any
non-reserved region.
Memory Models
CP/M-86is constructedas an 8080 Model. This means that all thesegment registers
are placed at the base of CP/M-86, and the CBIOS is identical in most respects to
that of CP IM-80 (with changes in instruction mnemonics, of course). In fact, the
only additions are found in the SETDMAB,
GETSEGB, SETIOB, and GETIOB
entry points in the BIOS, the additions for hard disk I/O, and the custom APC
features in the extended functions. The warm start subroutine is simpler since you
are not required to reload the CCP and BDOS under CP/M-86. If you implement
the IOBYTE facility,
you have to define the variable in your BIOS. Taking these
changes into account, you needonlyperforma simpletranslation of your CP/M-80
BIOS into 8086 code to implement the 8086 BIOS.
Disk Definition Tables
The disk definition tables included with CP /M-86 for the APC have been deve-
loped, configured,
and included in the CBIOS. Therefore, there is no need to
generate your own disk definition tables using GENDEF.
Bootstrap Operation
CP/M-86 resides on thefirst two tracks of the double-sided, double-densitysystem
distribution diskette.
It is loaded by a single step bootstrap loader operation.

CPIM-86System Overview
BDOS Calls
To make a BDOS system call, use the reserved software interrupt #224. The jump to
the BDOS at location 0005H found in CP/M-80 is not present in CP/M-86.
However, the address field at offset 0006 is present so that programs which "size"
available memory using this word value will operate without change. CP IM-80
BDOS functions use certain 8080 registers for entry parameters and returned
values. CP/M-86 BDOS functions use a table of corresponding 8086 registers. For
example, the 8086 registers CH and CL correspond to the 8080 registers Band C.
Look through the list of BDOS function numbers in Table 4-2. You'll find that
functions 0, 27, and 31 have changed slightly. Several new functions have been
added, but they do not affect existing programs.
Addressing
A
major difference between the two CP 1M operating systems is their approach to
addressing. In CP/M-80, all addresses sent to the BDOS are 16-bit values in the
range OOOOH to OFFFFH. In CP/M-86, the addresses are 16-bit offsets from the DS
(Data Segment) register, which is set to the base of your data area. If you translate
an existing CP/M-80 program to the CP/M-86 environment, the data segment is
fewer than 64K bytes. Therefore, the DS register does not have to be changed
following
intialload, and all CP IM-80 addresses becomesimple DS-relative offsets
in
CP/M-86.
Program Termination
Under CP/M-80, programs terminate in one of three ways:
• return directly to the CCP;
• call BDOS function 0;
• transfer control to absolute location OOOOH.
CP/M-86, however, supports only the first two methods of program termination.
Consequently, the
automatic disk system reset that follows ajump to OOOOH is not
performed. Instead, disk system reset is accomplished by entering a CONTROL-C
at the CCP level.
Many new facilities in CP IM-86 simplify programming and expand application
programming capability. CP/M-86 was designed to make it easy to get started. If
you are convertingfrom CP 1M -80 to CP 1M -86, there are no major changes beyond
the translation to 8086 machine code.
1-5

Chapter 2
Command Setup and
Execution Under CP 1M -86
This chapter discusses the operation of the Console Command Processor, the
format of transient programs, CP/M-86 memory models, and memory image
formats.
CCP BUILT-IN AND TRANSIENT COMMANDS
The operation of the CP/M-86 Console Command Processor (CCP) is similar to
that of CP/M-80's CCP. At initial cold start, it prints the CP/M sign-on message,
automatically logs in Drive A,
and issues the standard prompt at the console.
CP /M-86 then waits for input command lines from the console.
The
command line may include one of the built-in commands: DIR, ERA, REN,
TYPE,
or USER. (Note that SAVE is not supported under CP/M-86 since the
equivalent function
is performed by DDT-86.) See the CPIM-86 User's Guide for
the APC for more information
about these programs.
The
command line may also begin with the name of a transient program with the
assumedfile type
CMD, denotinga commandfile. The CMD file type differentiates
transient
command files used under CP/M-86 from COM files, which operate
under CP /M-80.
The CCP allows multiple programs to reside in memory, providing facilities for
background tasks. A transient program may load additional programs for execu-
tion under its own control.
2-1

Command Setup andExecution Under CP/ M-86
2-2
For example, a background printer spooler could first be loaded, followed by an
execution ofDDT-S6. DDT-S6 may, in turn, load a test program for a debugging
session
and transfer control to the test program between breakpoints. CP/M-S6
keeps track of the order in which programs are loaded and, upon encountering a
CONTROL-C, discontinues execution of the program most recently activated at
the CCP level. In this example, a CONTROL-C at the DDT-86 command level
aborts DDT-S6 and its test program. A second CONTROL-C at the CCP level
aborts the background printer spooler. A third CONTROL-C resets the disk
system.
Note that program abort due to CONTROL-C does not reset the disk system, as is
the case in CP/M-SO. A disk resetdoes not occurunless the CONTROL-C occurs at
the CCP command input level with no programs residing in memory.
When CP/M-S6 receives a request to load a transient program from the CCP or
another transient program, it checks the program's memory requirements. If suffi-
cient
memory is available, CP /M-86 assigns the required amount of memory to the
program and loads it. Once loaded, the program can request additional memory
from the BDOS for bufferspace. When the program is terminated, CP/M-S6 frees
both the program memory area and any additional buffer space.
TRANSIENT
PROGRAM EXECUTION MODELS
The initial values of the segmentregisters are determined by the memorymodelused
by the transient program and described in the CMD file header. The three memory
models are summarized in Table 2-1.
Table 2-1
CP/M-86 Memory Models
MODEL
GROUP RELATIONSHIPS
8080 Model
Code and data groups overlap
Small Model
Independent code and data groups
Compact Model
Three or more independent groups

Command Setup and Execution Under CPIM-86
The 8080 Model supports programs which are directly translated from CP IM-80
when code and data areas are intermixed. The 8080 model consists of one group
which contains all the code, data, and stack areas. Segment registers are initialized
to the starting address of the region containing this group. The segment registers
can, however, be managed by the application
program during execution so that
multiple segments within the code group can be addressed.
The SmallModel is similar to that defined by Intel, where the program consists of
independentcode and data groups. The Small Model is suitablefor use by programs
taken from CP IM-80 where code and data are easily separated. The code and data
groups often consist of, but are not restricted to, single 64K byte segments.
The Compact Model occurs when any of the extra, stack, or auxiliary groups is
present in a program. Each group may consist of one or more segments, but if any
group exceeds one segment in size, or if auxiliary groups are present, then the
application
program must manage its own segment registers during execution in
order to address all code and data areas.
In all three models, local stacks are requiredin user programs that makeBDOS calls
since the BDOS may change information in the system stack.
The three models differ primarily in the manner in which segment registers are~
initialized upon transient program loading. The operating system program load
function determines the memory model used by a transient program by examining
the program group usage, as described in the following sections of this chapter.
The 8080 Memory Model
The8080 Model is assumedwhen the transient program contains only a codegroup.
In this case, the CS, DS, and ES registers are initialized to the beginning of the code
group, while the
SS and SP registers remain set to a 96-byte stack area in the CCP.
The Instruction Pointer Register (IP) is set to 100H, as in CP IM-80, thus allowing
base page values
at the beginning of the code group. Following program load, the
8080 Model appears as shown in Figure 2-1, where low addresses are at the top of
the diagram.
2-3

Command Setup andExecution Under CPIM-86
2-4
SS:
SS + SP:
CS DS ES:
DS+OOOOH:
CS+OIOOH:
CCP
CCP Stack
base
page
IP = OIOOH
code
data
~
~
Figure 2-1 CP 1M -86 8080 Memory Model
The intermixed code and data regions are indistinguishable. The base page values,
described below, are identical to CP/M-80. This allows simple translation from
8080,8085, or Z80 code into the 8086 environment. The following ASM-86 example
shows how to code an 8080 Model transient program.
cseg
org
100h
(code)
endcs
equ
$
dseg
org
offset endcs
(data)
end