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.he TMS9900/99105 Cross-assembler Rev. 1.0 Page #
TMS9900/99105 Cross-assembler
Rev. 1.0
Derived from the original William C. Colley, III.
M6800 Cross Assembler
by
Alexander Cameron
Written and modified during June 1984.
The Manual Such As It Is.
.pa
.pn 1
.op
...COLUMNWIDTH 65
...MARGINWIDTH 6
...T1
1.1 Format of Cross-assembler Commands
...T2
1.1.1 Command Strings
To run the 9900 cross-assembler, type the
following command line:
A>a99 filename options
filename:
The name of the source input file is
filename.a99, the list can go to filename.l99,
and the hex file can go to filename.h99.
options: See next section.
...T2
1.1.2 Options
The source file comes from the currently
logged disk drive unless it is redirected by
putting the string "sd" in the options field.
s specifies the source file and d is a device
code from the following list:
a, b, c, d Disk drives.
- The currently logged in disk drive.
Lines of input containing errors will always
be output to the console device. If the full
listing is desired, it must be called for by
putting the string "ld" in the options field.
l specifies list file and d is a device code as
per the source file, or one of the following:
x Console device.
y List device.
The hex file will not be output unless called
for as per the list file.
Options must be run together into a single
string with no embedded blanks.
...T2
1.1.3 Examples
A>a99 barf source -- a:barf.a99
list -- none.
hex -- none.
A>a99 barf sblxha source -- b:barf.a99
list -- con:
hex -- a:barf.h99
A>a99 barf ly source -- a:barf.a99
list -- lst:
hex -- none.
A>b:a99 barf sbh- source -- b:barf.a99
list -- none.
hex -- a:barf.h99
...T1
1.2 Format of TMS9900 Cross-assembler Source Files
Lines of source input are terminated with CR/LF
pairs. Internally, the character before the LF
is discarded, so if the CR is missing, the last
character of the line will be eaten up. The
internal line buffer will hold a 120 character
line. This may be changed by altering the
"#define LINLEN 120" statement in xasm99.gbl
and recompiling the cross-assembler. Excess
characters in the line are thrown out.
Lower case letters are converted to upper
case in as few places as possible. They are:
1) In opcodes,
2) In checking for keywords such as NOT, and
3) In command strings.
This means that "not", "NOT", "Not", etc.
are all possible spellings of the logical
inversion operator. This also means that
"foo" and "FOO" are different symbols.
Watch this if you start encountering U errors
of symbols that you "know" you defined.
...T2
1.2.1 Statements
Source files input to the 9900 Cross-assembler
consist of statements of the form:
[label] [opcode] [arguments] [;comments.]
Labels are recognized by their beginning in
column 1. If it doesn't begin there, it is
assumed to be an opcode. Labels are
assigned the current program counter value
unless the line's opcode is "EQU" or "SET".
Opcodes may be either 9900 instruction
mnemonics or pseudo-ops.
The arguments following the opcode will vary
with the opcode. In the case of opcodes such
as "NOP", they may be absent entirely.
Lines terminate with either a CR/LF pair or a
semicolon that is not embedded in a quoted
string. Anything after a semicolon is ignored
by the assembler, but will appear in the
listing. Note that a semicolon in column 1
will make the entire line a comment.
...T2
1.2.2 Symbols
Symbols may be of any length, but only the
first 8 characters are significant. This
may be changed by changing the "#define
SYMLEN 8" statement in a68.gbl and
recompiling the assembler. Note that
this increases the storage required by the
symbol table as each entry in the symbol
table is SYMLEN+2 bytes in length. The
following characters are legal in a
symbol:
A-Z a-z ! & . : ? [ \ ] ^ _ `
{ | } ~ 0-9
Note that symbols may not begin with 0-9 as
this would make them impossible to distinguish
from Intel format numbers.
A special symbol $ is always equal to the
address of the first byte of code generated by
a given line.
...T2
1.2.3 Numeric Constants
Numbers begin with 0-9,%. % leading base
designator represent binary. If the number
begins with 0-9, the assembler looks for one
of the trailing base designators B, O, Q, D,
or H. If the number does not end with one of
these, it is assumed to be decimal. B is the
base designator for binary, O and Q are for
octal, D is for decimal, and H is for
hexidecimal. Trailing base designators and the
hex digits A-F can be in either upper or lower
case. Note that hex numbers that start
with A-F and are specified with the
designator H must have a leading zero added
to keep them from being mistaken for symbols.
For example:
0ff80h evaluate to ff80 hex.
128 and 128d evaluate to 80 hex.
35o, and 35q evaluate to 1d hex.
%0111000 and 0111000b evaluate to 39 hex.
A character constant is a string composed of
zero, one, or two ASCII characters, delimited
by either single or double quotes (' or ").
Note that single quotes only balance single
quotes, and double quotes only balance double
quotes. Thus a character constant of 22 hex
can be specified by '"'. For example:
"ab" evaluates to 6162 hex.
"" evaluates to 0000 hex.
"'" evaluates to 0027 hex.
'A' evaluates to 0041 hex.
Note that in the two-character character
constant, the left-hand character will appear
in the upper-order byte and the right-hand
character will appear in the lower-order byte.
...T2
1.2.4 Strings
Strings are formed in the same way as
character constants except that they may be of
any length up to and including 255 characters.
The first character will be placed in the
lowest-order memory byte. A line-feed
character may not be embedded in a string
as it terminates the line and will yield a
quote imbalance error. Note that strings
are only valid in the arguement field of an
"TEXT" pseudo-op.
...T1
1.3 Expression Evaluation
The following operators are allowed in
expressions. The operators are listed in order
of precedence.
Unary Plus, Unary Minus
*, /, MOD, SHL, SHR
+, -
>, >=, <, <=, <>, =
(These can also be written as
GT, GE, LT, LE, NE, EQ.)
NOT (1's complement)
AND (Bitwise logical AND)
OR, XOR (Bitwise logical OR and Exclusive
OR)
HIGH, LOW
Parentheses are used to change the order of
precedence. During evaluation of an
expression, as soon as a new operator is
encountered that has precedence less than or
equal to the last operator encountered,
all operations up to the new operator are
performed. That is, subexpressions
involving operators of higher precedence
are computed first.
All operators except +, -, *, /, =, <>, >=,
<=, >, < must be separated from their operands
by at least one space or tab.
The "HIGH mumble" is equivalent to "mumble SHR
8" and "LOW mumble" is equivalent to "mumble
AND 0ffH".
The relational operators (=, >, etc.) evaluate
to 0ffffh if the relationship is true, 0 if it
is false.
Expressions are terminated by commas,
semicolons, or CR/LF pairs.
...T1
1.4 990 Family Instructions
The instructions of the 9900/99105
microprocessor fall into several catagories.
Each requires a certain set of arguments and
disallows other arguments. Arguments may be
specified in any order and are separated by
commas Blanks may be used freely
throughout the argument field (except within
symbols or operators such as NOT) to enhance
the readability of the source code.
The basic syntax is as follows:
[label] LI R1,expression ;The expression
;is evaluated
;from left to
;right.
The type of addressing each instruction is
allowed along with the number of operands the
assembler expects the instruction to have, is
carried in the ATTRIB byte which is returned by
the GETOPC function. The ATTRIB byte is
is made up of two 4 bit nibbles the least
significat describing operand 1 and the most
significant describing operand 2. (See the
heading comments of GETOPC which is part of the
file A99TBLS.CSM). The ATTRIB byte will also
tell the assembler which one of the 7 basic
instruction formats a particulare instruction
falls into. Thes formats/groups are discussed
in the following sections.
...T2
1.4.1 Addressing Modes
The 9900/99105 instruction set allows 5 basic
addressing modes. These are:
Mode Example
---- -------
Workspace register MOV R1,R3
Workspace register indirect A *R1,R2
Symbolic CLR @expr
Indexed A @expr(R1),R2
Workspace register indirect DEC *R7+
(auto increment)
These modes will in general be written in the
form:
R, *R, *R+, @X, @X(R)
where R refers to a Register and X to an
address.
...T2
1.4.2 Instruction Formats
The assembler will properly evaluate 7 basic
instrucion formats; these are:
Format 0 - No operands at all (N)
Format 1 - R,*R,*R+,@X,@X(R)
Format 2 - Displacement (Disp)
Format 3 - Destination Field only (D)
Format 4 - Signed Displacement (SD)
Format 5 - Workspace Register (W or C)
Format 6 - Immediate Operands (IOP)
Format 7 - Bit Manipulation Instrucions
(TMS99105 only)
Depending on the instruction these formats may
lie within either the source or destination
fields.
...T2
1.4.3 Group 1 Instructions
This group contains the following opcodes:
NOP
RSET IDLE CKOF CKON LREX
RTWP
These opcodes permit no arguments, and hence
are of format 0.
...T2
1.4.4 Group 2 Instructions
This group of instructions are of Format type 1
and are Dual Operand Instructions with Multiple
Addressing Modes for Source and Destination
Operand.
This group contains the following opcodes:
A AB C CB S SB SOC SOCB
SZC SZCB MOV MOVB
Instruction format: [opcode|format1|format1]
Example: A *R1+,R2
...T2
1.4.5 Group 3 Instructions
This group of instructions are Dual Operand
Instructions with Multiple Addressing Modes for
the Source Operand and Workspace Register
Addressifng for the Destination.
This group contains the following opcodes:
COC CZC XOR MPY DIV XOP LDCR STCR
Instruction format: [opcode|format3|format1]
Example: XOP @LABEL,3
...T2
1.4.6 Group 4 Instructions
This group of instructions allow Multiple
Addressing modes for the source Operand, and
thus a single operand instructions.
This following instructions belong to this
group:
B BL BLWP CLR SETO INV NEG ABS SWPB
INC INCT DEC DECT X
BIND(a TMS99105 instruction)
Instruction format: [opcode|format1]
Example: INC @LABEL(R3)
...T2
1.4.7 Group 5 Instructions
This group of instructions are CRU Single-Bit
Instructions.
The following instructions belong to this
group:
SBO SBZ TB
Instruction format: [opcode|format4]
Example: SBO 25
1.4.8 Group 6 Instructions
This group covers the Conditional Jump
instrucions. Note that the maximum
displacement range is +127 to -128 words.
The following instructions belong to this
group:
JEQ JGT JH JHE JL JLE JLT JMP JNC JNE
JNO JOC JOP
Instruction format: [opcode|format2]
Example: JEQ LABEL
...T2
1.4.9 Group 7 Instructions
This group have an Immediate Source Operand
with an Workspace Register as the Destination
Operand.
The following instructions belong to this
group:
AI ANDI CI LI ORI
BLSK (a TMS99105 instruction)
Instruction format: [opcode|format5]
[ format6 ]
Example: AI R3,128
...T2
1.4.10 Group 8 Instructions
This group covers the Internal Register Load
Immediate Instructions and have an Immediate
Source Operand only.
The following instructions belong to this
group:
LWPI LIMI
Instruction format: [ opcode ]
[ format6 ]
Example: LIMI 3
...T2
1.4.11 Group 9 Instructions
This group covers the Internal Register Store
Instructions and have Destination Workspace
Register Addressing only.
The following instructions belong to this
group:
STST STWP
LST LWP ( TMS99105 instructions )
Instruction format: [opcode|format5]
Example: STST R3
...T2
1.4.12 Group 10 (TMS99105 only)
This group covers the Bit-Manipulation instruc-
tions peculiar to the TMS99105. This group has
a different instruction format than the basic
9900 set insofar as the format fields lie in
the 2nd word. The instructions in this group
are:
TMB TCMB TSMC
Instruction format: [ opcode ]
[ format3|format1]
Example: TMB @BITMAP(R3),8
...T1
1.5 Pseudo-operations
...T2
1.5.1 END
When this statement is encountered, the
assembler decides that the end of the
source file has been reached. If this
statement is missing or in a conditional
assembly block that is not being assembled, the
assembler will encounter end-of-file on the
source file. In this case, the assembler
will attach an END statement and will flag an
error. The syntax is as follows:
[label] END
If any IF statement is not closed with an ENDI
at this point, an error will be flagged.
This statement permits no arguments.
...T2
1.5.2 EQU
This statement is used to assign a permenant
value to a symbol. This value may not be
subsequently changed by a SET, another EQU, or
by writing the symbol in column 1 as a label.
The syntax is as follows:
label EQU expression
A phasing (P) error will result if any
forward references are encountered in the
evaluation of the expression.
...T2
1.5.3 BYTE
This statement is used to place bytes in
memory. Each byte is defined by an
expression. Multiple bytes can be defined by
expressions separated by commas. If an
expression evaluates to a quantity outside the
range -128 to 255, an error is flagged. The
syntax is as follows:
[label] BYTE [expr1][,epxr2].....
...T2
1.5.4 TEXT
This statement is used to place strings in
memory. Its arguments may only be strings.
Multiple strings may be placed in memory if
the strings are separated by commas. The
syntax is as follows:
[label] TEXT [string][,string].....
...T2
1.5.5 WORD
This statement is used to place words in
memory. Each word is defined by an
expression. Multiple words may be defined by
expressions separated by commas. Words are
placed in memory with their high-order byte in
the low-order memory location and the low-order
byte in the high-order memory location. The
syntax is as follows:
[label] WORD [expr1][,expr2].....
...T2
1.5.6 BSS (Block Starting with Symbol)
This statement is used to reserve a block of
memory for working storage, etc. It
requires one argument that gives the number of
bytes of storage to reserve. The syntax is
as follows:
[label] BSS expression
...T2
1.5.7 EVEN
This statement is used to force the assembler
to align code on an even word boundary if the
present programme counter is odd. If the
programme counter is odd a zero byte is output
if even the statement is ignored. The
assembler will also flag an error is an attempt
is made to output code to an odd address. The
syntax is as follows:
[label] EVEN
...T2
1.5.8 DXOP
This statement allows the programmer to define
their own macro instructions around the
Extended Operation Instruction (XOP). The
assemble will substitute the XOP code for a
given instruction in place of the name assigned
to the XOP. The syntax is as follows:
DXOP PUSH,3 ;assign the name PUSH to
;XOP number 3
For example if PUSH is a previously coded XOP
which pushes registers onto the stack then
instead of coding this XOP instruction as XOP
R3,3 you can code PUSH R3 - this will produce
the same code as XOP R3,3 but will generally
make the programme far more easy to follow.
The 990 CPU's allow up to 15 XOP's.
...T2
1.5.9 Conditional Assembly
Blocks of code can be assembled or not
assembled based on the value of some
expression. The basic syntax is as follows:
IF expression
(lines of code)
ENDI
If the expression evaluates to 0, the code
will not be assembled. The source lines will
be transfered to the listing, but no hex
output will be generated. It is recommended
that a value of $ffff be used for a true
value since it turns into a false value under
bitwise inversion.
In addition, the ELSE directive is
supported as follows:
IF expression
(lines of code)
ELSE
(more lines of code)
ENDI
This is equivalent to:
IF expression
(lines of code)
ENDI
IF NOT expression
(more lines of code)
ENDI
Note that labels are not permitted on
conditional assembly directives. Also note
that an END statement can fail to be
recognized if it is in a conditional assembly
block with a false expression.
A phasing (P) error will be flagged if there
are any forward references in the expression.
...T2
1.5.10 AORG
This statement is used to load a value
into the assembly program counter. The value
is obtained from the expression. If the
expression contains forward references, a
phasing (P) error will result. If a label is
present, it will be EQUed to the new program
counter value. The syntax is:
[label] AORG expression
...T2
1.5.11 SET
This statement is used to assign a temporary
value to a symbol. The symbol may not be
redefined by an EQU or by writing it in column
1 as a label, but it may be redefined by
another SET statement. The value for the
symbol is obtained from the expression. If it
contains forward references, a phasing (P)
error will result.
The syntax is:
label SET expression
...T1
1.6 Error Messages
Error messages are flagged with a single
letter in column 1 of the offending line in
the listing. The meaning of each letter
follows.
A Presently not implemented.
B Distance on a branch instruction
is too great. Use a jump
instruction with a branch around it,
or rearrange your code to shorten the
distance.
D Digit too large for the base was
encountered. In particular, watch
for 8 or 9 in an octal number and a-
f in a decimal number.
E Expression ill-formed. Look for non
arithmetic characters in indexed
addressing modes.
I If stack imbalance. Look for ELSE
or ENDI without an IF or an IF
still open at the end of the file.
L Invalid label. Label may contain
invalid characters or be equal to a
reserved word like NOT. Label may
be present on a conditional assembly
directive.
M Label multiply defined. Label
defined more than once and all
definitions are not SET statements.
O Invalid opcode. Look for
misspellings, missing semicolons, or
opcodes in column 1.
P Phasing error. Look for expressions
in ORG, EQU, SET, or IF
directives that contain forward
references. If none exist, something
wierd is going on as a label that was
defined in pass 1 mysteriously
vanished in pass 2.
R Register value too large. Registers
values between 0 and 15 only are
allowed. This error will most likely
occur if a register value is being
evaluated from an expression which
overflows.
S Syntax error. Check your syntax
against my samples.
T Too many arguments on this
line. WORD directives may only
define 127 words, while TEXT and
BYTE directives may only define 255
bytes. On other statements,
you put superfluous arguments on
the line.
U Undefined symbol encountered
during expression evaluation.
V Value out of bounds. In
particular, FCB expressions and 8-
bit immediate values must evaluate
to -128 to 255, while index values
must evaluate to 0 to 255.
* This statement generated by the
assembler. Right now, this only
happens if you drop an END
statement or remove it
through conditional assembly.
" Quote imbalance error. Bear in
mind that ' will not terminate a
string started with " and vice-
versa.
( Parenthesis imbalance error. Count
them!
...T1
1.7 Assembler Abort Conditions
Under certain circumstances, this assembler
will just give up and quit in the middle of an
assembly. If you don't get the error count
diagnostic on the console, read your screen
for sure! The following messages occur:
1) Can't open source.
The source file does not exist
on the specified disk drive.
2) Can't open list.
Can't open hex.
No directory entries left on the
disk drive in question.
3) Illegal command line.
Bone up on command lines.
4) No file info supplied.
Bone up on command lines.
5) If stack overflow.
IF directives may only be nested
16 deep. Rebuild your source
code to reduce your nesting depth,
or change the "#define IFDEPTH 16"
statement in xasm99.gbl and recompile
the assembler.
6) Disk read error.
Source file has a bad CRC or
some other difficulty.
7) Disk write error.
Out of disk or directory space on the
list or hex file.
8) Error closing file.
Problem closing list or hex
file. You shouldn't get this one.
9) Symbol Table Overflow.
Your source program defines too many
symbols. The current limit is 500.
If you have more memory than I do,
you can change the "#define SYMBOLS
500" line in a99.gbl and recompile
the assembler. Otherwise, you
must work on your source code.
...T1
1.8 Compiling the Assembler
To compile the assembler as it stands, you
will need the following items:
1) 40K of RAM.
2) The BDS C Compiler Version 1.5
(good box, Leor!!).
3) Digital Research's ASM or MAC
assembler. (Note: Only needed if
you want to play with the functions
in a99tbls.mac as they exist in a
form digestible by CLINK in the
file xasm99.crl.)
To get a99tbls.crl up from scratch, you
do the following. I assume all files
including ASM or MAC live on drive A.
A>casm a99tbls ;source a99tbls.csm
This should yield a file a99tbls.asm on drive A.
A>mac a99tbls $pz -s ;may use asm fn.aaz
A>cload a99tbls ;produce CRL file
You should now have a99tbls.crl on drive A.
Now you are ready to compile the rest of the
beast.
A>cc a99
A>cc a99asmlnc
A>cc a99evalc
A>cc a99getc
A>cc a99putc
A>cc a99symbc
Now you can link it all together.
A>clink a99 -s
*a99asmln
*a99eval
*a99get
*a99put
*a99symb
*a99tbls
And, as if by magic, you've got a99.com!
Note that the linkage can all be done on one
line, but my paper isn't wide enough here to
do it that way. Note that if you have more
than 40K of RAM, you may want to increase
your symbol table size. Symbols are 10 bytes
each, so plan accordingly.
...T1
1.9 Final Comments
Happy assembling! If you have questions or
note any bugs, I'd appreciate a shout
at (617)258-1204, (617)266-3179 or on the
Boston CBBS at (617)963-8310. The questions
will point up weaknesses in the manual, and
the bugs need to be stamped upon unmercifully.
