Matrix Orbital LCD0821 Legacy - Manual (Page 22)

LCD0821 rev 2 22
6. Appendix: Command Summary
6.1 General
The operation of the LCD0821 is controlled by a simple and consistent command set. Commands control
text display
graphics display
miscellaneous operating parameters
This chapter includes summary tables of all commands. Individual commands are discussed in detail in
Chapters 3 and 4 in the same sequence as in the following tables.
6.2 Issuing Commands
Commands are issued to the LCD0821 by the controller. In a test setup, commands can be issued to the
LCD0821 by means of a BASIC program, using the chr$( ) function. In the tables below, we've shown
commands in hex, ASCII and decimal form. All commands begin with the prefix character 0xFE (254
decimal). These commands are issued on the serial communications link (I
2 C or RS-232) at the currently
defined baud rate.
For example (using BASIC in a test setup), you could issue the command to clear the screen on the
LCD0821 by including the line:
PRINT#1,chr$(254);chr$(88)
in your BASIC program.
6.3 On Numbers
Like all computerized devices, the LCD0821 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:
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.