From: Steve Judd (sjudd_at_ffd2.com)
Date: 2009-01-03 18:18:45
Hi,
Catching up on 9 months of unread email...
On Mon, 13 Oct 2008, Vanessa Ezekowitz wrote:
> Now, I can't say whether a backslash is the ideal character... Looking
at the docs for Sirius (Steve Judd's 65816 assembler), < ! and > are
what he uses to force 8, 16, and 24-bit operands, respectively, when used
with absolute addressing.
From the W65C816S data sheet, section 7, "Recommended W65C816S Assembler
Syntax Standards":
7.3.3.5 In any location in an operand where an address, or expression
resulting in an address, can be coded, the assembler shall recognize the
prefix characters <, |, and >, which force one byte (direct page), two
byte (absolute), or three byte (long absolute) addressing. In cases where
the addressing modes is not forced, the assembler shall assume that the
address is two bytes unless the assembler is able to determine the type of
addressing required by context, in which case that addressing mode will be
used. Addresses shall be truncated without error in an addressing mode is
forced which does not require the entire value of the address. For
example, LDA $0203 and LDA |$010203 are completely equivalent. If the
addressing mode is not forced, and the type of addressing cannot be
determined from context, the assembler shall assume that a two byte
address is to be used. If an instruction does not have a short addressing
mode (as in LDA < which has no direct page indexed by Y) and a short
address is used in the operand, the assembler shall automatically extend
the address by padding the most significant bytes with zeroes in order to
extend the address to the length needed. As with immediate address, any
expression evaluation shall take place before the address is selected;
thus, the address selection character is used only once, before the
address of expression.
7.3.3.6 The ! (exclamation point) character should be supported as an
alternative to the | (vertical bar).
-S
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