VK202-25 rev. 05
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7. Appendix: Command Summary
7.1 General
The operation of the VK202-25 is controlled by a simple and consistent command set. Commands control
text display
graphics display
keypad interface
miscellaneous operating parameters
This chapter includes summary tables of all commands. Individual commands are discussed in detail in
Chapters 3 to 5 in the same sequence as in the following tables.
7.2 Issuing Commands
Commands are issued to the VK202-25 by the controller. In a test setup, commands can be issued to the
VK202-25 by means of a BASIC program, using the chr$( ) function. In the tables below, we've shown
commands in hex, ASCII and decimal form. All commands begin with the prefix character 0xFE (254
decimal). These commands are issued on the serial communications link (I
2
C or RS-232) at the currently
defined baud rate.
For example (using BASIC in a test setup), you could issue the command to clear the screen on the VK202-
25 by including the line:
PRINT#1,chr$(254);chr$(88)
in your BASIC program. Or with C you could (using Zcomm serial library)
ZComm1->WriteCommByte(0xfe);
ZComm1->WriteCommByte('X');
7.3 On Numbers
Like all computerized devices, the VK202-25 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
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