On 02/12/2011 04:33 AM, Oliver Seitz wrote:
I have not tried it, though, and sometimes I come to wrong conclusions.
Transients on the data line could perhaps affect USART worse than SPI. I
wouldn't ignore vasiles warning.
Ah well... I just found it interesting. I certainly wasn't planning on
using RS232 for such transfers.
Daisy-chain is to connect a device's input to the previous device's output, and
its output to the next device's input, eventually forming a circle. PATA is a
bidirectional bus, you can't daisy-chain it.
When I think of "daisy-chain"... my initial thoughts are of the original
"daisy-chain" gadgets... SCSI drives.
SCSI is bi-directional... and didn't always "form a circle", calling
into question your claim about not being able to daisy-chain it.
So you would have to connect 16 data lines and 3 address lines to all drives, and a dedicated read and write line to each Master/Slave
pair. Read and Write are a kind of, in this case, device select lines. Bus control is usually either done via a clock (or strobe) and a
"Read/not Write" line, or by one "Read" and one "Write" line. Here's the latter case. The "Read"
and "Write" line are the "ChipSelect" function you expected to find on the CS lines.
Ah... that makes more sense.
If speed is of no great concern, and when switching from one drive to another
it *can not* be a great concern as you will have to re-initialize the
filesystem anyway, you can use ... port expanders, shift registers,... to get
more pins. But for the read and write signals, speed *does* matter. Use the
expanded port pins to control some e.g. 74HC4066 that switch your pic's read
and write lines to the desired hard disk pair.
I have no real interest in anything beyond 4 drives per PIC chip.
If I want more drives... I can easily add up 4 more at one time by just
adding an addition dual bus IDE controller to the SPI line.
4 drives is plenty to start with.
If neither the read nor the write line is asserted, the drive is in HI-Z.
Ah... ok.
Thanks for taking the time to explain.
Lyos Gemini Norezel
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