OverviewCommand Line Invokation
Syntax
Directives
Numbers
Expressions
String Expressions
Native Opcodes
Enhanced Opcodes
Output Files
Overview
Meaning
kexpr
expr
sexpr
Command Line Invokation
Switches
Output Files
Use With ICEbreaker
Syntax
Labels
@ Labels
? Labels
Statements
Comments
Differences To MPASM
There are numerous differences in what PICASM will accept and what MPASM will,
however, many source files for MPASM will compile without alteration; this is
based upon a selection of real source code examples run through PICASM. These
code examples have been created by third parties without knowledge of PICASM
and are therefore representative of code which is actually being written, rather
than what MPASM supports.
MPASM is a very comprehensive assembler, and I have no hesitation in
recommending it if you wish to use the native instruction set only. MPASM
does not however support the same enhanced instruction set that PICASM does,
and the penalty for using the enhaced instruction set ( or PICASM at all ) is a
divergence away from the MPASM standard.
The important places where changes may need to me made to the source are as
follows -
MACRO
The syntax of the MACRO directive has changed, as has the means of handling
arguments passed into the MACRO. Please see the section on the MACRO
directive for full details of the new use.
LOCAL
Local labels are no longer declared using the LOCAL directive, but are
defined by prefixing the label with a question mark ( '?' ). Labels so
defined will be local to the MACRO within which they are declared, or
the source file within which they appear.
LIST
RADIX and Number Format
The RADIX directive is no longer supported. All numbers are deemed to be
decimal unless they have been defined using a radix overide ( H'..' etc ),
and when the enhanced assembly mode has not been selected, all numbers
which start witha zero ( '0' ) are deemed to be hexadecimal.
END
The end directive is simply ignored when the native assembly option is
selected.
Directives
PROCESSOR
HIDDEN
LIST
NOLIST
INCLUDE
IF
IFDEF
Shorthand version of IF DEFINED(sexpr).
IFNDEF
Shorthand version of IF NOT DEFINED(sexpr).
SELECT
There are two type of SELECT statements; SELECT and SELECT CASE. Both are
terminated by ENDSELECT or END SELECT and enclose a number of CASE statements.
The SELECT statement will chose to assemble the code preceeded by the CASE
statement which yields a true ( non-zero ) result.
A EQU 2
SELECT
CASE A = 1
DATA "A is 1"
CASE A = 2
DATA "A is 2"
CASE ELSE
DATA "A is neither 1 or 2"
END SELECT
Only one CASE must evaluate true ( non-zero ) in a SELECT statement.
The CASE ELSE statement will be executed if no other CASE match has occured.
The CASE ELSE statement cannot be followed by any subsequent CASE statements.
The "CASE" in a SELECT CASE is optional, SELECT followed by an expression is
treated as a SELECT CASE.
SELECT CASE
There are two type of SELECT statements; SELECT and SELECT CASE. Both are
terminated by ENDSELECT or END SELECT and enclose a number of CASE statements.
The SELECT CASE statement will chose to assemble the code perceeded by the CASE
statement whose result matches the expression specified at the end of the SELECT
CASE satement
A EQU 2
SELECT CASE A
CASE 1
DATA "A is 1"
CASE 2
DATA "A is 2"
CASE ELSE
DATA "A is neither 1 or 2"
END SELECT
Only one CASE must match with the expression in a SELECT CASE statement.
The CASE ELSE statement will be executed if no other CASE match has occured.
The CASE ELSE statement cannot be followed by any subsequent CASE statements.
The "CASE" in a SELECT CASE is optional, SELECT followed by an expression is
treated as a SELECT CASE.
MACRO
EQU
label EQU expr
regbit EQU reg,{-}bit
regbit EQU regbit
reg EQU REG reg
SET
REG / RES / DIM
reg REG { size } { @ address }
reg REG EQU reg
DATA
The DATA statement is used to store numbers and strings within the code space.
The data statement is followed by one or more expressions and strings, each
separated by commas.
Each number is stored as a single word.
Each string has its separate characters stored in the order in which they appear
in the string.
A string may be PACKED, in which case two characters are stored in each word
if the opcode size is 14-bits or more. The first character of the string is
stored in the msb part of the word, the next in the lsb and so on. The string
will be padded with a NULL (zero) character if it has an odd number of
characters. Strings are not NULL terminated except when explicitly specified
as such by the user.
If the opcode size is 14 or 15 bits, the characters will be truncated to 7-bit
by ignoring the msb of each character and will be aligned to use the 14 lsb's
of the opcode word.
END
MODULE
ORG
/
Directives can be specified at the command line or in the source code by
using /option.
Whether an option has been set or not can be determined by using the
DEFINED symbol function. The option must be enclosed in quotes,
IF DEFINED "/LOCAL"
DATA "/LOCAL set"
ELSE
DATA "/LOCAL not set"
END IF
IFDEF "/LOCAL"
DATA "/LOCAL set"
ELSE
DATA "/LOCAL not set"
END IF
Note that not enclosing the variable name you are checking for in quotes will
cause a confusing, but correct, error message
IF DEFINED FRED
^ Not defined (FRED)
/NATIVE Allow Microchip native opcode assembly
/ENHANCED ALLOW ENHANCED OPCODE ASSEMBY
/LIST:ALL SHOW EVERYTHING IN LISTING
/LIST:SYSTEM SHOW SYSTEM SYMBOL TABLE
/LIST:BALANCE SHOW SYMBOL TABLE BALANCE
/LIST:CODE SHOW ASSEMBLED CODE IN LISTING
/LIST:NATIVE SHOW NATIVE OPCODE LIST IN LISTING
/PASS2 FORCE PASS2 PROCESSING EVEN IF ERRORS
/FILE:SYM PRODUCE .SYM FILE
/NOTIDY DON'T DELETE TEMPORARY FILES AT END OF COMPILATION
/ICEBREAKER MODIFY TARGET TO TAKE INTO ACCOUNT IT'S RUNNING ON ICEBREAKER
/ICD Allw ICD registers etc to be used
/NOHEX NO HEX OUTPUT FILE
/PROCESSOR:cpu TYPE OF CPU ( READ ONLY )
Numbers
Enhanced Number Format
Native Number Format
Expressions
Variables
Pre-Defined Number Variables
* Current PC
Variable Indexing
expr[kexpr]
Binary Operators
Unary Operators
USED("name")
This is used to determine if the named label or variable has been referenced in
the program but has not been defined. This is extremely useful when writing
library functions based upon whether a call has been made to a function of not,
allowing library files to only include code which has been referenced.
BSR MyLib
; More code
IF USED("MyLib")
MyLib:
; Perform the actions required by MyLib
RTS
END IF
The MyLib code from the library will only be included if the program
references MyLib and it hasn't been defined within the program before
the library code is referenced.
String Expressions
String Variables
Pre-Defined String Variables
DATE$
TIME$
TITLE$
FILE$
Binary String Operators
Unary String Operators
Native Opcodes
Enhanced Opcodes
Pre-Defined Registers
Pre-Defined Bits
Branching Across Page Boundaries
Output Files
.LST - Listing File
.ERR - Error File
.HEX - Object File
.COD - Code Debugging File
