Banking

monitor.c

@@ -91,14 +91,15 @@ static uint8_t split_line(char *line, char **argv)
 static void print_help(void)
 {
     bios_puts(
-        "Commands (hexadecimal numbers):\r\n"
-        "  D|DUMP address [length]   Dump memory (default 0040, max 0100)\r\n"
-        "  W|WRITE address byte ...  Write one or more memory bytes\r\n"
-        "  I|IN port                 Read an I/O port\r\n"
-        "  O|OUT port byte           Write an I/O port\r\n"
-        "  G|GO address              Execute code; RET returns here\r\n"
-        "  B|BASIC                   Start ROM Tiny BASIC at 1000\r\n"
-        "  H|HELP|?                  Show this help\r\n");
+        "Commands (hex numbers):\r\n"
+        " D addr [len]  Dump memory\r\n"
+        " C start end   16-bit checksum, inclusive\r\n"
+        " W addr byte... Write memory\r\n"
+        " I port        Read I/O\r\n"
+        " O port byte   Write I/O\r\n"
+        " G addr        Execute\r\n"
+        " B             Tiny BASIC\r\n"
+        " H             Help\r\n");
 }
 
 static void command_dump(uint8_t argc, char **argv)
@@ -131,6 +132,28 @@ static void command_dump(uint8_t argc, char **argv)
     }
 }
 
+static void command_checksum(uint8_t argc, char **argv)
+{
+    uint16_t address;
+    uint16_t end;
+    uint16_t checksum = 0;
+
+    if (argc != 3 || !parse_hex(argv[1], &address) ||
+        !parse_hex(argv[2], &end) || end < address) {
+        bios_puts("Usage: C start end\r\n");
+        return;
+    }
+
+    for (;;) {
+        checksum = (uint16_t)(checksum + *(volatile uint8_t *)address);
+        if (address == end) break;
+        ++address;
+    }
+
+    print_hex16(checksum);
+    bios_puts("\r\n");
+}
+
 static void command_write(uint8_t argc, char **argv)
 {
     uint16_t address;
@@ -222,6 +245,8 @@ static void execute_line(char *line)
         print_help();
     } else if (strings_equal(argv[0], "d") || strings_equal(argv[0], "dump")) {
         command_dump(argc, argv);
+    } else if (strings_equal(argv[0], "c") || strings_equal(argv[0], "checksum")) {
+        command_checksum(argc, argv);
     } else if (strings_equal(argv[0], "w") || strings_equal(argv[0], "write")) {
         command_write(argc, argv);
     } else if (strings_equal(argv[0], "i") || strings_equal(argv[0], "in")) {