Reset with Isolated RS-232

Discussion specific to the DIP and TQFP packaged ZX devices like the ZX-40, ZX-44, ZX-32 and ZX-328 series. The differences between these devices is primarily the packaging and pinout so most issues will apply to all devices.
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dlh
Posts: 395
Joined: 15 December 2006, 12:12 PM
Location: ~Cincinnati

Reset with Isolated RS-232

Post by dlh »

I'm using an Analog Devices ADM3251E isolated single channel RS232 Line Driver/Receiver which only has RX/TX so I'll need to use the API to initiate downloads as well as reset a ZX-328n.

What should I do with the reset pin? 10K pullup?
dkinzer
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Location: Portland, OR

Re: Reset with Isolated RS-232

Post by dkinzer »

dlh wrote:What should I do with the reset pin? 10K pullup?
That sounds about right. There is an internal pullup on the reset line but I think that it is in the high 10's of KOhms. I feel more comfortable with a lower resistance on the reset line so I usually add an external pullup of 10K or so.
- Don Kinzer
dlh
Posts: 395
Joined: 15 December 2006, 12:12 PM
Location: ~Cincinnati

Post by dlh »

Thanks, Don.

After reading the datasheet and seeing the ADM3251E uses 300MHz for the isolated voltage supply, with a 6-layer PCB recommended to reduce EMI, I decided to go with opto-isolators, for fear the 300MHz will wreak havoc with the 310MHz superregenerative RF receiver onboard the device being modified. I still need to handle reset & d/l with the API as the opto-isolator circuit steals power from DTR.
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