{"id":968,"date":"2022-10-19T08:25:22","date_gmt":"2022-10-19T00:25:22","guid":{"rendered":"https:\/\/qaqaq.top\/?p=968"},"modified":"2022-11-27T12:43:52","modified_gmt":"2022-11-27T04:43:52","slug":"arm-cortex-m3-4-%e8%bf%9b%e4%bd%8d-%e5%80%9f%e4%bd%8d%e4%b8%8e%e6%ba%a2%e5%87%ba","status":"publish","type":"post","link":"https:\/\/qaqaq.top\/?p=968","title":{"rendered":"[ARM-Cortex-M3\/4] \u8fdb\u4f4d\/\u501f\u4f4d\u4e0e\u6ea2\u51fa"},"content":{"rendered":"\n
\"\"<\/div><\/figure>\n\n\n\n

1.1 \u8fdb\u4f4d\u4e0e\u501f\u4f4d
\u8fdb\u4f4d\u4e0e\u501f\u4f4d\u662f\u65e0\u7b26\u53f7\u6570\u800c\u8a00\u7684\u3002<\/p>\n\n\n\n

\u8fdb\u4f4d\uff1a\u65e0\u7b26\u53f7\u6570\u76f8\u52a0\u65f6\uff0c\u6700\u9ad8\u6709\u6548\u4f4d\u5411\u66f4\u9ad8\u4f4d\u8fdb\u4f4d\uff0c\u8868\u793a\u65e0\u7b26\u53f7\u6570\u8fd0\u7b97\u53d1\u751f\u4e0a\u6ea2\u51fa\u3002
\u501f\u4f4d\uff1a\u65e0\u7b26\u53f7\u6570\u76f8\u51cf\u65f6\uff0c\u6700\u9ad8\u6709\u6548\u4f4d\u5411\u66f4\u9ad8\u4f4d\u501f\u503c\uff0c\u8868\u793a\u65e0\u7b26\u53f7\u6570\u8fd0\u7b97\u53d1\u751f\u4e0b\u6ea2\u51fa\u3002
ARM\u72b6\u6001\u5bc4\u5b58\u5668CPSR\u7684C\u4f4d\u8868\u793a\u8fdb\u4f4d\u6216\u975e\u501f\u4f4d\u6807\u5fd7\uff08Carry\/borrow flag\uff09<\/p>\n\n\n\n

\u52a0\u6cd5\u6307\u4ee4\u4e2d\uff08\u5305\u62ec\u6bd4\u8f83\u6307\u4ee4CMN\uff0c\u6839\u636e\u4e24\u6570\u76f8\u52a0\u7ed3\u679c\u8fdb\u884c\u6bd4\u8f83\uff09\uff0c\u5f53\u7ed3\u679c\u4ea7\u751f\u4e86\u8fdb\u4f4d\uff0c\u5219C = 1 \uff0c\u5176\u4ed6\u60c5\u51b5C = 0\uff1b\uff08\u8fdb\u4f4d\u6807\u5fd7\uff0c\u53d1\u751f\u8fdb\u4f4d\u65f6C=1\uff09
\u5728\u51cf\u6cd5\u6307\u4ee4\u4e2d\uff08\u5305\u62ec\u6bd4\u8f83\u6307\u4ee4CMP\uff0c\u6839\u636e\u4e24\u6570\u76f8\u51cf\u7ed3\u679c\u8fdb\u884c\u6bd4\u8f83\uff09\uff0c\u5f53\u7ed3\u679c\u53d1\u751f\u9519\u4f4d\uff0c\u5219C = 0 \uff0c\u5176\u4ed6\u60c5\u51b5C = 1\uff1b\uff08\u975e\u501f\u4f4d\u6807\u5fd7\uff0c\u53d1\u751f\u501f\u4f4d\u65f6C=0\uff09
\u5bf9\u4e8e\u5305\u542b\u79fb\u4f4d\u64cd\u4f5c\u7684\u975e\u52a0\/\u51cf\u6cd5\u8fd0\u7b97\u6307\u4ee4\uff0cC\u4e3a\u6700\u540e\u4e00\u6b21\u88ab\u6ea2\u51fa\u7684\u4f4d\u7684\u6570\u503c\u3002
\u5bf9\u4e8e8\u4f4d\u65e0\u7b26\u53f7\u6570\uff080~255\uff09\uff1a<\/p>\n\n\n\n

58\uff0b124\uff1d182\uff0c\u8303\u56f4\u5185\uff0c\u65e0\u8fdb\u4f4d
170\uff0b124\uff1d294\uff0c\u8303\u56f4\u5916\uff0c\u6709\u8fdb\u4f4d<\/p>\n\n\n\n

1.2 \u6ea2\u51fa
\u6ea2\u51fa\u662f\u6709\u7b26\u53f7\u6570\u800c\u8a00\u7684\uff0c\u5373\u8fd0\u7b97\u7ed3\u679c\u8d85\u51fa\u6700\u5927\u8303\u56f4\u3002\u53ea\u6709\u5f53\u4e24\u4e2a\u76f8\u540c\u7b26\u53f7\u6570\u76f8\u52a0\uff0c\u800c\u8fd0\u7b97\u7ed3\u679c\u7684\u7b26\u53f7\u4e0e\u539f\u6570\u636e\u7b26\u53f7\u76f8\u53cd\u65f6\uff08MSB\u4e3a\u7b26\u53f7\u4f4d\uff09\uff0c\u4ea7\u751f\u6ea2\u51fa\u3002\uff08\u4e24\u4e2a\u6b63\u6570\u76f8\u52a0\u6216\u6b63\u6570\u51cf\u8d1f\u6570\u3001\u4e24\u4e2a\u8d1f\u6570\u76f8\u52a0\u6216\u8d1f\u6570\u51cf\u6b63\u6570\uff1b\u5bf9\u4e8e\u4e00\u6b63\u4e00\u8d1f\u76f8\u52a0\u5219\u4e0d\u53ef\u80fd\u51fa\u73b0\u6ea2\u51fa\uff09<\/p>\n\n\n\n

CPSR\u7684V\u4f4d\u8868\u793a\u6ea2\u51fa\u6807\u5fd7\uff08oVerflow flag\uff09\uff1a<\/p>\n\n\n\n

\u5728\u52a0\/\u51cf\u6cd5\u8fd0\u7b97\u6307\u4ee4\u4e2d\uff0c\u5f53\u64cd\u4f5c\u6570\u4e0e\u8fd0\u7b97\u7ed3\u679c\u4e3a\u4e8c\u8fdb\u5236\u7684\u8865\u7801\u8868\u793a\u7684\u5e26\u7b26\u53f7\u6570\u65f6\uff0cV = 1\u8868\u793a\u7b26\u53f7\u4f4d\u6ea2\u51fa\u3002\u5982\uff1a\u4e24\u4e2a\u6b63\u6570\u6267\u884cADDS\u6307\u4ee4\u540e\uff0c\u548c\u8fd0\u7b97\u7ed3\u679c\u7684MSB\u4e3a1\uff08\u89c6\u4e3a\u8d1f\u6570\uff09\uff0c\u5219\u53d1\u751f\u6ea2\u51fa\u3002<\/p>\n\n\n\n

\u5bf9\u4e8e8\u4f4d\u6709\u7b26\u53f7\u6570\uff08-128~127\uff09\uff1a<\/p>\n\n\n\n

\uff0d86\uff0b124\uff1d28 \uff0c\u8303\u56f4\u5185\uff0c\u65e0\u6ea2\u51fa
58\uff0b124\uff1d182 \uff0c\u8303\u56f4\u5916\uff0c\u6709\u6ea2\u51fa
\u6ce8\u610f<\/strong>\uff1aC<\/code>\u548cV<\/code>\u6807\u5fd7\u4f4d\u7684\u5229\u7528\u7531\u7a0b\u5e8f\u5458\u6765\u51b3\u5b9a\uff0c\u5373\u82e5\u8ba4\u4e3a\u64cd\u4f5c\u6570\u4e3a\u65e0\u7b26\u53f7\u6570\uff0c\u5219\u5173\u5fc3C<\/code>\u6807\u5fd7\uff1b\u82e5\u8ba4\u4e3a\u64cd\u4f5c\u6570\u4e3a\u6709\u7b26\u53f7\u6570\uff0c\u5219\u5173\u5fc3V<\/code>\u6807\u5fd7\u3002<\/p>\n\n\n\n

\"\"<\/div><\/figure>\n\n\n\n

\u5c06\u64cd\u4f5c\u6570\u89c6\u4e3a\u65e0\u7b26\u53f7\u6570\uff0c\u6d4b\u8bd5C<\/code>\u6807\u5fd7<\/p>\n\n\n\n

\u52a0\u6cd5\u6307\u4ee4<\/strong>\uff1a<\/p>\n\n\n\n

\u6574\u6570\u72b6\u6001\u6807\u5fd7\u4f4dcmn r0, r1<\/code>\u00a0<==>adds r2, r0, r1<\/code><\/p>\n\n\n\n

ldr\t\tr0, =0x80000000\t\r\nldr\t\tr1, =0x70000000\r\nadds\tr2, r0, r1\t\t;\u6700\u5927\u503c\u4e3a0xffffffff\u672a\u53d1\u751f\u8fdb\u4f4d, c = 0, \u4f46MSB\u4e3a1, \u5219n = 1\u8868\u8d1f\u6570\r\n\r\nldr\t\tr0, =0x80000000\r\nldr\t\tr1, =0x80000000\r\nadds\tr2, r0, r1\t\t; \u7ed3\u679c\u4e3a[0]\u8868\u793a\u8fdb\u4f4d c = 1\r\n\r\nldr\t\tr0, =-3\t\t;\u8865\u78010xfffffffd\r\nldr\t\tr1, =-2\t\t;\u8865\u78010xfffffffe\r\nadds\tr2, r0, r1\t;\u8d1f\u6570\u8865\u7801\u76f8\u52a0, \u7ed3\u679c\u4e3a0xfffffffb\uff0c\u663e\u7136\u53d1\u751f\u4e86\u8fdb\u4f4d\uff0c C = 1\r\n<\/code><\/pre>\n\n\n\n
\u51cf\u6cd5\u6307\u4ee4<\/strong>\uff1a<\/p>\n\n\n\n
\u6574\u6570\u72b6\u6001\u6807\u5fd7\u4f4dcmp r0, r1<\/code>\u00a0<==>subs r2, r0, r1<\/code><\/p>\n\n\n\n
ldr\t\tr0, =123\r\nldr\t\tr1, =100\r\nsubs\tr2, r1 ,r0\t;\u7ed3\u679c\u4e3a-0x17\uff0c\u5176\u8865\u7801\u4e3a0xffffffe9, \u53d1\u751f\u501f\u4f4d C=0\r\nsubs\tr2, r0 ,r1\t;\u7ed3\u679c\u4e3a0x17, \u672a\u53d1\u751f\u501f\u4f4d C=1\r\n<\/code><\/pre>\n\n\n\n
\u5c06\u64cd\u4f5c\u6570\u89c6\u4e3a\u6709\u7b26\u53f7\u6570\uff0c\u6d4b\u8bd5V<\/code>\u6807\u5fd7<\/p>\n\n\n\n
; \u6b63\u6570 + \u6b63\u6570 (MSB = 0)\r\nldr\t\tr0, =0x70000000\r\nldr\t\tr1, =0x70000000\r\nadds\tr2, r1 ,r0\t; \u9ad8\u4f4dMSB=1\uff0c\u6ea2\u51fa, v = 1\r\n; \u6b63\u6570 - \u8d1f\u6570 (\u6b63\u6570 + \u6b63\u6570 )\r\nldr\t\tr0, =0x80000000\r\nldr\t\tr1, =0x70000000\r\nsubs\tr2, r1 ,r0\t;\u6ea2\u51fa v = 1\r\n; \u8d1f\u6570 - \u6b63\u6570 (\u8d1f\u6570 + \u8d1f\u6570)\r\nsubs\tr2, r0 ,r1\t;\u6ea2\u51fa v = 1\r\n; \u8d1f\u6570 + \u8d1f\u6570 (MSB = 1)\r\nldr\t\tr0, =0x80000000\r\nldr\t\tr1, =0x80000000\r\nadds\tr2, r0 ,r1\t; \u7ed3\u679c\u4e3a0, \u5373MSB=0,  \u6ea2\u51fa v = 1\r\n<\/code><\/pre>\n\n\n\n
3 \u603b\u7ed3
\u65e0\u7b26\u53f7\u6570\u5728\u76f8\u52a0\u65f6\u624d\u4f1a\u53d1\u751f\u8fdb\u4f4d\uff0c\u76f8\u51cf\u53d1\u751f\u501f\u4f4d\uff1b
\u6709\u7b26\u53f7\u6570\u53ea\u6709\u5728\u4e24\u6b63\u6570\u6216\u8d1f\u6570\u76f8\u52a0\u65f6\uff08\u51cf\u6b63\u6570\u53ef\u89c6\u4f5c\u52a0\u8d1f\u6570\uff0c\u51cf\u8d1f\u6570\u89c6\u4f5c\u52a0\u6b63\u6570\uff09\u624d\u4f1a\u53d1\u751f\u6ea2\u51fa\uff0c\u5176\u4ed6\u60c5\u51b5\u4e0d\u4f1a\u6ea2\u51fa\uff1b
\u7531\u4e8e\u6c47\u7f16\u4e0d\u80fd\u771f\u6b63\u533a\u522b\u6709\u7b26\u53f7\u4e0e\u65e0\u7b26\u53f7\u6570\uff0c\u4e00\u822c\u7531\u7a0b\u5e8f\u5458\u4e3b\u89c2\u51b3\u5b9a\uff0c\u5bf9\u4e8e\u65e0\u7b26\u53f7\u6570\u5173\u5fc3C\u4f4d\uff0c\u6709\u7b26\u53f7\u6570\u5219\u5173\u5fc3V\u4f4d\u3002
\u6570\u5b57\u5728\u8ba1\u7b97\u673a\u4e2d\u662f\u4ee5\u5176\u8865\u7801\u8fdb\u884c\u5b58\u50a8\u7684\uff0c\u6b63\u6570\u7684\u8865\u7801\u4e3a\u5176\u672c\u8eab\uff0c\u8d1f\u6570\u7684\u8865\u7801\u4e3a\u539f\u7801\u6309\u4f4d\u53d6\u53cd+1\u3002
END<\/p>\n","protected":false},"excerpt":{"rendered":"
1.1 \u8fdb\u4f4d\u4e0e\u501f\u4f4d\u8fdb\u4f4d\u4e0e\u501f\u4f4d\u662f\u65e0\u7b26\u53f7\u6570\u800c\u8a00\u7684\u3002 \u8fdb\u4f4d\uff1a\u65e0\u7b26\u53f7\u6570\u76f8\u52a0\u65f6\uff0c\u6700\u9ad8\u6709\u6548\u4f4d\u5411\u66f4\u9ad8\u4f4d\u8fdb\u4f4d\uff0c\u8868\u793a\u65e0\u7b26\u53f7\u6570\u8fd0\u7b97 […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[23],"tags":[57],"class_list":["post-968","post","type-post","status-publish","format-standard","hentry","category-23","tag-57"],"_links":{"self":[{"href":"https:\/\/qaqaq.top\/index.php?rest_route=\/wp\/v2\/posts\/968"}],"collection":[{"href":"https:\/\/qaqaq.top\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/qaqaq.top\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/qaqaq.top\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/qaqaq.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=968"}],"version-history":[{"count":1,"href":"https:\/\/qaqaq.top\/index.php?rest_route=\/wp\/v2\/posts\/968\/revisions"}],"predecessor-version":[{"id":972,"href":"https:\/\/qaqaq.top\/index.php?rest_route=\/wp\/v2\/posts\/968\/revisions\/972"}],"wp:attachment":[{"href":"https:\/\/qaqaq.top\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=968"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/qaqaq.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=968"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/qaqaq.top\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=968"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}