YSS952 datasheet(60/116 Pages) YAMAHA

60 / 116 page

3 FUNCTION DESCRIPTION

YSS952

6SS952A30

3.4.3

The Host Controller Requests to MDSP2 Processing

The host controller uses MDSPREF [7:0] and MDSPDAT [7:0] to send requests to MDSP2 processing programs.

MDSPREQ [7:0] is 0x00 when there's no request pending.

The host controller program and a MDSP2 program can assign and use values in 0x01 through 0xFF in

MDSPREQ [7:0] for their agreed upon requests. MDSPDAT [7:0] is used for transferring data of those requests.

In the following example, how a request—MDSPREQ [7:0]=0x01, defined and used to transfer data in

MDSPDAT [7:0] written by the host controller to a MDSP2 firmware—is handled by a handshaking protocol is

illustrated.

[Note 1] When values of 0x01 through 0xFF in MDSPREQ [7:0] are assigned and used for the host

controller–MDSP2 command request, each request requires a dispatching code segment in MDSP2

firmware.

[Note 2] While waiting for MDSPREQ [7:0]==0x00 indication from MDSP2, the host controller can attend

other tasks than the polling.

MDSPREQ[7:0] == 0x00？

Writes 0x01 to MDSPREQ[7:0].

Reads MDSPREQ[7:0].

Reads MDSPDAT[7:0] to obtains the data.

Writes 0x00 to MDSPREQ[7:0].

YES

MDSPREQ[7:0] == 0x00？

YES

MDSPREQ[7:0] == 0x01?

End

Handled by the host processor

Handled by the MDSP2 firmware

Start

Reads MDSPREQ[7:0].

Writes MDSPDAT[7:0].

Reads MDSPREQ[7:0].

YSS952 Datasheet(PDF) 60 Page - YAMAHA CORPORATION