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- .\" $Header$
- .TH 6500_AS 1
- .ad
- .SH NAME
- 6500_as \- assembler for Mostek 6500
- .SH SYNOPSIS
- /usr/em/lib/6500_as [options] argument ...
- .SH DESCRIPTION
- This assembler is made with the general framework
- described in \fIuni_ass\fP(6).
- .SH "SEGMENTS and TYPES"
- An additional segment, the \fIzeropage\fP, can be started by the
- \&\fI.zero\fP pseudo-instruction.
- Some adressing-modes require an address between 0 and 255.
- Such an address must be defined with the means of the \fI.zero\fP
- pseudo-instruction.
- A plain number between 0 and 255 is not allowed.
- The assembler will complain that it must be a zero page expression.
- .IP example
- \&.zero
- .br
- answer: .space 1
- .br
- \&.text
- .br
- and (answer, x)
- .SH SYNTAX
- .IP expressions
- An two-byte expression followed by the pseudo-operator \fI.h\fP (\fI.l\fP)
- has the value of the higher (lower) byte of the expression.
- \&\fI.h\fP and \fI.l\fP bind stronger than all other operators.
- E.g. -1.h parses as -[1.h] which has value 0.
- You have to write [-1].h to get 0xFF.
- .IP "addressing modes"
- .nf
- .ta 8 16 24 32 40 48
- syntax meaning (name)
- #expr 8-bit value (immediate)
- expr address (direct)
- expr, x expr + contents of x
- or or
- expr, y expr + contents of y
- yields address (indexed)
- (expr) address of address (only with JMP) (indirect)
- In the next two addressing modes `expr' has to be
- a zeropage expression.
- (expr, x) expr + contents of x
- yields address (pre-indexed indirect)
- (expr), y contents of expr + contents of y
- yields address (post-indexed indirect)
- .fi
- .IP instructions
- There are two mnemonics that do not map onto one machine-instruction:
- `add' and `sub'. `Add mode' maps onto `clc; adc mode'.
- `Sub mode' maps onto `sec; sbc mode'.
- .SH "SEE ALSO"
- uni_ass(6),
- ack(1)
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