Guess the Micro

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#1
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Based on the enclosures here
Any guess as to what this microprocessor is? I suspect it is
One-time programmable
18 pin
Has no on-board EEPROM
Has I/O ports apparently named PA0..PA7.
PA4 can wakeup the microprocessor
A port bit PB2 exists

It's within a garage door is open transmitter sold by Chamberlain and Sears

In the photo, the microprocessor, U2 in the schematic, is a chip underneath the round blob of epoxy. The 8 pin IC is the EEPROM.

(disclaimer: The attached documents came from the public-access FCC web site)

Attachment(s): 

Last Edited: Sun. Mar 28, 2010 - 12:42 AM
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I can't see anything in those PDFs.

Leon Heller G1HSM

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Leon,

They open up OK for me.

Ross

Ross McKenzie ValuSoft Melbourne Australia

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The 338A011 looks like one of those inscrutable "programmed at the factory" part numbers.

Jim

 

Until Black Lives Matter, we do not have "All Lives Matter"!

 

 

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It looks PIC'ish to me. The position of the OSC, Vdd & Vss seem very familiar as to how Microchip do things. Microchip encouraged ASIC design with their wafers.

The RF part does not inspire me with it's ability to maintain a repeatable frequency!

Crook is it Steve?

Charles Darwin, Lord Kelvin & Murphy are always lurking about!
Lee -.-
Riddle me this...How did the serpent move around before the fall?

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I had to download the schematic, I couldn't open it directly.

It's definitely not a PIC. The pins don't seem in the right places, PICs don't have a separate Int connection, and Microchip has always called Reset MCLR.

Leon Heller G1HSM

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Some device from Holtek, Taiwan, which has a whole range of OTP devices:

http://www.holtek.com.tw/pdf/uc/48x050608_1v151.pdf

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Yes, Holtek. I've noted in the past that they are in a lot of low cost remote controls. Their HT48xxx seems to match the schematic. I wonder what IC package is under the epoxy blob in the photo? Not a DIP. Do they epoxy it to stop code-theft?

Yes, rather primitive transmitter oscillator. So to is the receiver, sans much selectivity.

Also wondering about 312MHz versus US FCC. I thought the unlicensed band was 434, maybe 315, not 312.

In any event, these do send a unique ID code for several hundred feet, reliably.

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This is the COB (Chip-On-Board) "package" - the epoxy drop straight over the silicon chip.

Warning: Grumpy Old Chuff. Reading this post may severely damage your mental health.

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stevech wrote:
Yes, Holtek. I've noted in the past that they are in a lot of low cost remote controls. Their HT48xxx seems to match the schematic. I wonder what IC package is under the epoxy blob in the photo? Not a DIP. Do they epoxy it to stop code-theft?

The epoxy is the package. They just mount the silicon die on PCB with glue or something, bond the silicon connections to PCB pads and put some epoxy over it. Cheap. Technique has got to be at least 20 years old.

Now the question is why do you ask? Do you want to read the code or replicate the functionality with AVR or what?

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(Hobby thing).
I'm looking to modify these things for a different use. These units are appealing because they are really inexpensive/mass produced.

Last Edited: Sun. Mar 28, 2010 - 07:10 PM
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It's called chip-on-board. The PCB software I use has a special option for designing boards using it.

Leon Heller G1HSM

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What do these COB's use for the interconnects? Flying wires? Some sort of SMD?

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http://www.lmgtfy.com/?q=chip-on...

:D:D

(actually, I didn't know about it either - but now I know why all those LCD interface boards have got epoxy blobs on them)

Last Edited: Sun. Mar 28, 2010 - 08:23 PM
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They are connected the same way that die are connected to lead frames when chips are packaged, using gold or aluminium wires and ultrasonic welding.

Leon Heller G1HSM

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stevech wrote:
Yes, Holtek. I've noted in the past that they are in a lot of low cost remote controls. Their HT48xxx seems to match the schematic. I wonder what IC package is under the epoxy blob in the photo? Not a DIP. Do they epoxy it to stop code-theft?

Yes, rather primitive transmitter oscillator. So to is the receiver, sans much selectivity.

Also wondering about 312MHz versus US FCC. I thought the unlicensed band was 434, maybe 315, not 312.

In any event, these do send a unique ID code for several hundred feet, reliably.

In the US FCC part 15 allows the use of any frequency from 270MHz to about 450MHz - there is nothing special about 315MHz. In the rest of the world 418MHz and now 433MHz are special spot frequencies for suc huse.

kevin

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Thanks Kevin.
I think there are pretty severe FCC transmitter duty cycle limitations in these lower freqs too - since $3 garage door openers and outdoor thermometers can't listen before transmitting (CSMA).