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Subject: Re: Feature freeze - silent play (wasRe: #673350 'Improvements for status line')
From: Björn Stenberg (bjorn_at_haxx.se)
Date: 2003-04-11


Mike Holden wrote:
> My remaining issue is "Silent Play".

I believe silent play is an mpeg issue (misinterpreting vbr headers etc) and not a disk reading issue. I also haven't seen any reports about this since Linus fixed some problems in the mpeg code a while ago. Feel free to brief us if this happens to you.

> The code comment has 5 * nop, and the comments says 400ms. Where did this
> figure come from? Is it the ATA spec? How long does a nop take,

Yes, the 400ns is defined in the PIO protocol part of the ATA specification:

"HPIOI1: Check_Status State:
This state is entered when the host has written a PIO data-in command to the device and nIEN is set to one, or when INTRQ is asserted.
When in this state, the host shall read the device Status register. When entering this state from the HI4 state, the host shall wait 400 ns before reading the Status register."

A nop instruction takes one clock cycle, and since the cpu is clocked at 12 MHz each cycle is 83ns long.

-- 
Björn



Page was last modified "Jan 10 2012" The Rockbox Crew
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