Matrix Orbital LCD2041 Legacy - Manual (Page 24)

commands in hex, ASCII and decimal form. All commands begin with the prefix character 0xFE (254
decimal). These commands are issued on the serial communications link (I
2 C or RS-232) at the currently
defined baud rate.
For example (using BASIC in a test setup), the user could issue the command to clear the screen on the
display by including the line:
PRINT#1,chr$(254);chr$(88)
in the BASIC program.
ZComm1->WriteCommByte(0xfe);
ZComm1->WriteCommByte(’X’);
6.3 On Numbers
Like all computerized devices, the display operates with commands and values in the form of binary
numbers. These binary numbers are arranged in 8 digit (i.e., 8 bit) groups called bytes. The decimal value
of a byte may have any value from 0 to 255. Bytes are usually specified in either decimal or hexadecimal
(base 16) form for convenience, since binary numbers are confusing to deal with directly. Hexadecimal
(hex) numbers are particularly convenient because exactly two hexadecimal digits make up one byte, each
hex digit representing 4 binary digits (4 bits) as shown here;
Table 8: Hex Value Table
Binary Hex Decimal Binary Hex Decimal
0000 0 0 1000 8 8
0001 1 1 1001 9 9
0010 2 2 1010 A 10
0011 3 3 1011 B 11
0100 4 4 1100 C 12
0101 5 5 1101 D 13
0110 6 6 1110 E 14
0111 7 7 1111 F 15
Based on the table, the byte 01001011 can be represented in hex as 4B, which is usually written as any
of 4Bh, 4BH, 4B hex or 0x4B. The numbers can also be expressed in decimal form if preferred.
6.3.1 ASCII Characters
Since computers deal internally with numbers only, but externally with both letters and numbers, several
schemes were developed to ’map’ written characters to numeric values. One such scheme has become
universal, the American Standard Code for Information Interchange, or ASCII. ASCII tables are readily
available from a number of sources. A few examples will do here;
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