YMF721 Datasheet, PDF (16/41 Pages) LSI Computer Systems – FM + Wavetable Synthesizer LSI

YMF721
6-3-2. Resume
Command and Response have the following formats.
Command
E1h
0x00
data_0
..........
data_n
checksum
Command byte
Sub Command
data
.......
last data
checksum
Response
None
For Resume, data following the sub command are transmitted as seven bit data. Thus, it is necessary
to send the data obtained with suspend command to the internal processor after encoding it.
Checksum is determined so that the result of logical product (AND) of 7Fh and the sum of sub
command byte, encoded data and checksum becomes "0". The internal processor returns to the state
immediately before execution of Command E0h when it confirms that the data has been received
normally.
6-3-3. Others
YMF721(OPL4-ML2) can use the following special commands that do not send response.
1) Command FDh : Power down mode
Refer to 5-1.
When the power down command FDh has been written into the command register, do not write
any command before the return command to the control register has been executed.
2) Command FEh : Checking operating state of internal processor
This command is used to check if the internal processor is operating normally.
The internal processor is deemed operating normally if GBUSY bit of Status register is "0".
3) Command FFh : Discontinuing command execution
This command is used to discontinue the execution of a command. This command can be used
only when another command is being executed.
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July 10, 1997