I'm wondering why the read-strobe line is more of the problem and it appears that the write_strobe isn't affected.
The reason CF read strobe needs signal conditioning but not write strobe is because data corruption is caused by the read activities of CF drive. Another word, it is the simultaneous transition of multiple data lines from CF fast drivers that generates the worst amount of noise AND it is the fast response of CF's read strobe input that most readily affected by that noise. To elaborate, when CF read strobe is asserted, 8 or 16 CF data lines are driving simultaneously; the worst case is when data bus went from all zeros to all ones. All outputs want to go high, really fast, pushing against the capacitive data bus, so if there are significant resistance and inductance on the ground return, the CF ground will sink below the reference ground. All this is happening when CF read strobe is asserting low which has lower noise margin. When the CF ground sunk to -1.5V even briefly, the responsive CF read strobe would see a corresponding +1.5V spike which causes it to advance the FIFO to next data.
In the case of CF write, it is the slow retro computer driving 8-bit data bus with CF write strobe still negated high which has good noise margin. By the time CF write strobe is asserted, everything is quiet and stays quiet for hold time period after the negation of write strobe.
Having ground plane absolutely help mitigating the noise problem, but if you are using an CF adapter, you need to examine the ground traces from your quiet ground plane to CF disk ground. Sadly the cheap adapter readily available on eBay has not done a good job with ground returns.
The lesson here is mixing today's technology with yesterday's technology can be troublesome--not to yesterday's technology, but to today's technology.
Bill
