Maker Pro
Maker Pro

IDE/ATA interface open/totem?

U

Uns Lider

Jan 1, 1970
0
Is the IDE/ATA 40pin idc connector on modern (Pentium and up) computers open
collector type or totempole type ?

It's tristate.

-- uns
 
It's tristate.

I thought if there are no ide/ata units attached if it's possible to hook up a
TTL output to one of the data pins directly to sample with software a la
inw(0x1F0) without blowing up something.. ?
 
U

Uns Lider

Jan 1, 1970
0
I thought if there are no ide/ata units attached if it's possible to hook up a
TTL output to one of the data pins directly to sample with software a la
inw(0x1F0) without blowing up something.. ?

Are you sure you're not thinking of the parallel printer port?

Before all the UDMA stuff, cheap IDE cards used to connect the data lines
of the IDE cable directly to the data lines of the ISA bus through 330-ohm
resistors.

If you look at one of the more recent ATA specifications (draft versions
should be available on the net) there's a table of what types of drivers
are to be used on each pin. The data lines are all tristate, some of the
other lines can be totem-pole or open-collector. And some of them have
pullup resistors, while others have pulldowns. What a mess.

-- uns
 
Are you sure you're not thinking of the parallel printer port?
Before all the UDMA stuff, cheap IDE cards used to connect the data lines
of the IDE cable directly to the data lines of the ISA bus through 330-ohm
resistors.
If you look at one of the more recent ATA specifications (draft versions
should be available on the net) there's a table of what types of drivers
are to be used on each pin. The data lines are all tristate, some of the
other lines can be totem-pole or open-collector. And some of them have
pullup resistors, while others have pulldowns. What a mess.

Well kludge on kludge.. :)
But given the more or less ready to use databus on ata it's tempting to hook
simple things up .. ;-) it's not however any bus I would invest in seriously.

SCSI is certaninly more robust. I'm considering it since 10 Mbyte/s
(scsi2 fast) ain't too bad with simple ttl outputs, maybe even 20MHz narrow
could work?. However scsi certainly _will_ require a cpu to controll things as
opposed to "smart logic" wich can be enough on ide.
 
Top