SIO Maximum Current Draw?

[c0nsumer]

Can someone point me to any docs detailing the maximum current draw peripherials should put on the 5V rail on an SIO bus?

 

I'm working on an SIO2SD enhancement and I'm trying to decide if it should be bus powered or have an external supply.

 

(The external supply would allow for easy optoisolation, backlit LCDs, possibly VFDs, etc.)

Edited February 13, 2010 by c0nsumer

[candle]

its just a matter on how much current track on pcb can conduct since there is no other circuity involved

i would not use more than half of what is left from standard power supply when atari is up and running

[phaeron]

Page 146 of the OS manual says 50ma on pin 10.

[spookt]

Can someone point me to any docs detailing the maximum current draw peripherials should put on the 5V rail on an SIO bus?

 

I'm working on an SIO2SD enhancement and I'm trying to decide if it should be bus powered or have an external supply.

 

(The external supply would allow for easy optoisolation, backlit LCDs, possibly VFDs, etc.)

 

Mmm - VFDs

[c0nsumer]

Page 146 of the OS manual says 50ma on pin 10.

 

Thank you. And per this copy the 12V line (pin 12) is "...of unknown current rating...".

 

I think external is the only way to go in this case.

 

(I didn't expect this to be in an OS manual because this is hardware, not the OS...)

Edited February 14, 2010 by c0nsumer

[kurtm]

Page 146 of the OS manual says 50ma on pin 10.

 

Thank you. And per this copy the 12V line (pin 12) is "...of unknown current rating...".

 

I think external is the only way to go in this case.

 

(I didn't expect this to be in an OS manual because this is hardware, not the OS...)

 

And I'm fairly certain that 12V line supplies nothing on XL/XE machines (considering that except for the 1200xl, they all use a 5V power supply). And where I've found that a 1200xl will run on a 9VDC PS I'm betting it just regulates it down to 5V, unlike the 400/800 that use the 9VAC to get 12V and 5V.

[candle]

1200XL runs from 9V AC! and there are 2 5V regulators inside

beside this - if unmodded - it will supply no more than this 50mA manual states

 

as for XL/XE line - i don't know for sure, but i highly doubt that XC12 tape recorder will draw only 50mA

[c0nsumer]

Hmm. Well, that settles it then. The SIO2SD NUXX (or whatever it gets called) will get its own power supply, and I'll likely optically couple it to the SIO bus, just for added isolation.

[candle]

there is no need for optocoupling but external psu will prevent atmega chips from beign accidently erased

[+wood_jl]

I love reading techno-babble, and obviously you guys are way over my head, but a couple comments:

 

1) Oh no! More NUXX stuff coming, More to buy? [secretly means....OHHHHH YEAAAAAAAH!]

 

2) What's the deal with accidentally erasing ATmega chips if you don't use external power supply? Sdrive is ok, no??????

 

Thanks!

[c0nsumer]

there is no need for optocoupling but external psu will prevent atmega chips from beign accidently erased

 

It'll also let me use higher power displays.

 

I figure that since optocoupling is only another chip or so, why not? Then there won't be any concern with ground loops or anything like that either.

[c0nsumer]

1) Oh no! More NUXX stuff coming, More to buy? [secretly means....OHHHHH YEAAAAAAAH!]

 

Don't hold your breath. I'm still identifying parts and stuff. I announced the SDrive NUXX when it was much further along than this, and I'm much busier with day-job stuff now, unfortunately.

 

2) What's the deal with accidentally erasing ATmega chips if you don't use external power supply? Sdrive is ok, no??????

 

The SIO2SD's original fuse recommendation didn't include brown-out detection. If the power dipped a bit low, the flash on the chip (I believe) could become corrupt and it'd have to be reflashed in order to work again. Simply turning on brown-out detection stepped around this.

 

For the SDrive and SDrive NUXX BOD is enabled, so it's not a concern. This isn't something that one would usually have a problem with, but it could happen.

[atariksi]

Page 146 of the OS manual says 50ma on pin 10.

 

Thank you. And per this copy the 12V line (pin 12) is "...of unknown current rating...".

 

I think external is the only way to go in this case.

 

(I didn't expect this to be in an OS manual because this is hardware, not the OS...)

 

Here's my thoughts: It's in the OS manual because after having implemented the first ever screen saver (see location 77,78,79 in Mapping the Atari), they were about to implement the first ever power management system by controlling the current allowed for via a memory mapped control register but it never fructified. That and controlling that GTIA color control pot through some 4-bit control register would have been awesome. The latter would have allowed for 16 different 256 color palettes (for a total of 4096 colors) as well as not having to adjust the color POTs manually when switching GTIA chips from different systems.

[eed002]

The 800XL schematics show the SIO 5V supply line directly connected to the 5V supplied by the external power supply, so 1.5A....working on a similar SIO device, and had the same question.

 

-Ed

Edited July 13, 2018 by eed002

[BillC]

The 800XL schematics show the SIO 5V supply line directly connected to the 5V supplied by the external power supply, so 1.5A....working on a similar SIO device, and had the same question.

 

-Ed

The limit for external +5V current on the SIO port would NOT be 1.5A, it would be the maximum the power supply could deliver minus the current needed to run the computer.

[Faicuai]

Cannot tell about the max. draw, but a guaranteed 0.7w to 1.2w can be delivered (for sure) to any telepowerd SIO device.

[1050]

The 1050 schematics show that the +5 Volt READY line

is sapped for all of 0.34 ma and they will not work

sometimes if a 1200XL still has it's R63 at 100 ohms

supplying the +5 Volt READY line.

 

Voltage drop across 100 ohms with 0.34 ma draw is

0.034 volt and that much will neuter the goose entirely.

So good luck trying to draw over 4 thousand times that

much and still have it work with any other SIO device.

 

Maybe want to avoid not working issues and treat the

+5 Volt READY line as it was intended - with the lightest

of touch possible because you are not the only one needing

to use the signal.

 

There is no power available on the SIO cable, only signals

live here. Use the READY line for power and all other

devices go to sleep by design. How compatible did you

want your device to be?

[_The Doctor__]

that's why service centers took the current limiting resistors out and replaced them with protection diodes with super low voltage drop... or sometimes ...*gasp* jumped the resistor entirely...