YMF721 datasheet(15/41 Pages) LSI

15 / 41 page

YMF721

July 10, 1997

- 15 -

6-2. Command/Response register

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

Command/Response Port (R/W):

port

D6D5D4D3D2D1D0

OPL_Base + 6

Command Write

OPL_Base + 6

Response Read

Command Write...

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

Response Read...

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.

6-3-1. Suspend information

Command and response have the following formats.

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.

Command

Sub Command Command Length Response Length

Function

E0h

1 byte

variable

Reading suspend information

E1h

00h

variable

Resume

FDh

1 byte

Moving into power down mode

FEh

1 byte

Checking operating conditions

FFh

1 byte

Discontinuing command execution

Command

Response

E0h

Command byte

FFh

Response 1st byte

length L

data length (lower 8bit)

length H

data length (upper 8bit)

data_0

data

...........

.......

data_n

last data

checksum

checksum (8 bit)

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