《Freescale 汇编语言源程序标准》.doc

行的长度: ???为了便于阅读和打印,Freescale使用mono-spaced字体,这种字体每个字符宽度相等.字体大小是9?point;最大行长为70个字符. 示例如下: ;????????1?????????2?????????3?????????4?????????5?????????6?????????7 ;234567890123456789012345678901234567890123456789012345678901234567890 asc2hex:????bsr???ishex???????;check?for?valid?hex?#?first ????????????bne???dunA2asc????;if?not?just?return ????????????cmp???#’9’????????;check?for?A-F?($41-$46) ????????????bls???notA2F??????;skip?if?not?A-F 列表输出文件示例如下: ;????????1?????????2?????????3?????????4?????????5?????????6?????????7?????????8?????????9 ;23456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123 ??551?C1D7?AD?EA?????asc2hex:????bsr???ishex???????;check?for?valid?hex?#?first ??552?C1D9?26?0A?????????????????bne???dunA2asc????;if?not?just?return ??553?C1DB?A1?39?????????????????cmp???#’9’????????;check?for?A-F?($41-$46) ??554?C1DD?23?02?????????????????bls???notA2F??????;skip?if?not?A-F 从以上可以看出列宽最大到93字符,因为列表输出文件并不能给读者提供更多的有用信息,因此Freescale最大用到每行93字符. ----------------------------------------------------------- 避免使用TAB字符 ????TAB字符在不同的字处理软件中有不同的含义,当把源文件提交给其它文档时可能会出现问题,所以要避免使用TAB,而用多个空格代替. ----------------------------------------------------------- 源程序列分配 ???源程序由标号,助记符,操作数和注释组成一行; ???标号在第1列开始 ???指令助记符在第13列开始 ???操作数在19列开始 ???注释在31列开始;如果操作数超过了30列,注释必须和操作数的最后一个字符分开1到2个空格. ???如果一个标号超过11个字符,就应该另起一行,并在31列做注释.短标号也可以另起一行来突出它,这经常用在一个子程序开始处.见图3 ;????????1?????????2?????????3?????????4?????????5?????????6?????????7 ;234567890123456789012345678901234567890123456789012345678901234567890 label:??????mne???operand?????;comment ????????????brset?very,long,operand???;comment?can’t?start?in?col?31 veryLongLabel:????????????????;long?label?on?separate?line ????????????nop???????????????;instruction?with?no?operands short:????????????????????????;short?label?may?use?a?separate?line ????????????mne?operand???????;code?to?which?‘short’?refers ----------------------------------------------------------- 大写和小写字符 ???源程序中协调一致的大