Which shield wires to which GND pins on PATA 40-pins 80-wires connector - Page 1
Forum section: electronics / projects

author: ricko_uk
author_rank: Super Contributor
timestamp: May 31, 2022, 10:24:16 pm
content: Hi,The 80-wires ATA/PATA hard drive ribbon cables use a 40-pins IDC connector. Either the even or the odd wires are used for crosstalk reduction. i.e. every other wire is connected to GND. Apparently this is done through a third centre-row of insulator-displacement set of connector "blades".I cannot find whether that third row that connects all the odd (or even) wires to ground is connected to only one ground pin of the 40-pins IDC connector or to all GND pins of the ATA pinout...?If only to one or two, which ones?Does anybody know for sure? There must be some kind of standard or official documentation but cannot find it.I would like to use this cable for a system and want to make sure that if I use some of the ground pins as signal they are not shorted within the connector itself (by the third row of insulator-displacing "blades")...Thank you

author: coromonadalix
author_rank: Super Contributor
timestamp: June 01, 2022, 02:32:15 am
content: its not 80 wires its a 40 wires going into an40 pins idc connector, or you have the 44 pins connector too, normally its a simple straight flat cable connectorI did saw in the past some 80 pins SCSI cables, some of them where twisted in pairs (seen very rarely) normally you end them with an passive or acitve loadback to the main topics, its a simple straight cable, and you define the use of it the way you want ita good approach would be 1 data pin, 1 ground, 1 data pin etc ... an ground wire between 2 data etc ...I've seen some special cable with an shield around the flat cable BUT theses had an added ground wire to the ground body / case

author: DavidAlfa
author_rank: Super Contributor
timestamp: June 01, 2022, 02:56:30 am
content: https://jack.logicalsystems.it/homepage/techinfo/pinouts.asp?Code=cabdts_ata66_100

author: ricko_uk
author_rank: Super Contributor
timestamp: June 01, 2022, 03:51:48 pm
content: @David, that's exactly what I was looking for, thank you!it does look like the hardwired connections of all the even or odd pins to ground is hard-wired to some specific pins.@coromonadalix, I know what you are thinking but the cable I am referring to (albeit not very common anymore) is the one David pusted the link to. I didn't know it was referred to as "ATA 66/100 cable".

author: DavidAlfa
author_rank: Super Contributor
timestamp: June 01, 2022, 04:31:59 pm
content: I think coromonadalix got confused.IDE has always had 40 "signal" wires, but ATA/ATAPI/IDE/whatever standard will only work faster than 33MHz with 80 wires.As you said, the 80 wires improve the signal integrity, reducing crosstalk/coupling (shielding) by interleaving signal/gnd/signal/gnd... thus allowing faster signals.Check ATAPI-4 (Max 33MHz) and ATAPI-5 (Which introduced 66MHz and 80 wires), later standards improved up to 133MHz (edit: It seems they also made a rare 166MHz version, never saw it anywhere), but all using 80 wires.Still, it was pretty common to use 40 wires for CD/DVD drives, 80 wires weren't required as their speeds wouldn't saturate a 33MHz bus, and the cables were cheaper. Fastest DVD: 16x * 1385KB = ~22MB/s

author: ricko_uk
author_rank: Super Contributor
timestamp: June 01, 2022, 05:12:56 pm
content: Thank you David

author: coromonadalix
author_rank: Super Contributor
timestamp: June 01, 2022, 06:47:20 pm
content: oh that one indeed sorry lollI'm getting too old loll saw theses one only once