Sensoray 7429 - Manual (Page 18)

C OMMANDS
The great versatility of the 7429 is due to its simple but powerful set of built-in com-
mands. Commands vary in length depending on the need for supplementary parame-
ters. Some commands cause the coprocessor to return data to the host processor. The
first byte of each command typically adheres to this format:
Format of first command byte
Each command in the 7429's repertoire consists of at least one byte. Some commands
require more than one byte because the information necessary to process the command
will not fit into a single byte. Without exception, the first byte of each command con-
tains a 4-bit opcode within the four most significant bits.
The remainder of this chapter discusses the coprocessor command set. Each command
function is described, and the command and command-response byte strings affiliated
with each command are detailed. These conventions are used in describing commands
and responses:
1. A byte is represented by data contained in parenthesis.
2. Individual bits within a byte are separated by commas.
3. The suffix "H" on any datum designates hexadecimal notation.
4. Byte strings are depicted as bytes separated by commas.
5. A command consists of an ordered byte string to be written into the 7429's
command register.
6. A command response consists of an ordered byte string to be read from the
7429's data register.
7. The ordering of bytes in any byte sequence (command or response) is sacred.
8. Don't care bits within a byte are designated by "x".
D7 D6 D5 D4 D3 D2 D1 D0
OPCODE CHANNEL