> > The pins are the same, no matter if they are > configured as SPI or USART. (I2C can be different, e.g. > limited slew rate). The usualy given maximum speed for RS232 > thinks of +/-12V levels, plugs, and cabling outside a > device. There are limits, and I wouldn't try more than > 115kBaud then. But if the signals stay on one PCB, there is > no real difference between USART and SPI regarding > transmission speed. > > > > Makes sense.
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. > I was thinking more of a "daisy-chain" setup for PATA. 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. > The control lines in the schematic I linked before were A0, > A1, A2, Read, and Write. 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. > nearing the limit of a 40 pin device. 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'm not sure a "HI-Z" state on the control pins would work > for pata drives... but it'd be worth investigating. If neither the read nor the write line is asserted, the drive is in HI-Z. Greets, Kiste -- You received this message because you are subscribed to the Google Groups "jallib" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/jallib?hl=en.
