YMF721 Datasheet, PDF(15/41 Page) LSI Computer Systems

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YMF721 Datasheet, PDF (15/41 Pages) LSI Computer Systems – FM + Wavetable Synthesizer LSI

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YMF721

6-2. Command/Response register

I/O port for power down and suspend/resume register is described here.

Command/Response Port (R/W):

port

OPL_Base + 6

Command Write

Response Read

Command Write...

Response Read...

An interrupt occurs when data has been written into this register.

Response to a command is read from this register.

Note :

For the details of Command/Response, refer to 6-3.

6-3. Details of command register

Some of commands supported in the command register are as follows.

Command Sub Command Command Length Response Length

Function

E0h

E1h

00h

FDh

1 byte

variable

1 byte

variable

Reading suspend information

Resume

Moving into power down mode

FEh

1 byte

Checking operating conditions

FFh

1 byte

Discontinuing command execution

6-3-1. Suspend information

Command and response have the following formats.

Command

E0h

Command byte

Response

FFh

length L

length H

data_0

...........

data_n

checksum

Response 1st byte

data length (lower 8bit)

data length (upper 8bit)

data

.......

last data

checksum (8 bit)

Checksum is determined so that lower eight bits of the sum of values from length L to checksum

becomes "0".

The state of internal processor immediately before execution of this command can be resumed by

writing the data that is read into the internal processor by using resume command described below.

- 15 -

July 10, 1997

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