I need to acquire the CERDIP version of the PIC16C74B or a suitable replacement. - Page 1
Forum section: electronics / general

author: Dukov Ahzrukhal
author_rank: Regular Contributor
timestamp: October 12, 2019, 08:59:18 pm
content: Hello everyone, I find myself in quite a predicament. I have chosen the PIC16C74B MCU for a project. However, this chip is one time programmable and so debugging has quickly gotten expensive. Since this is for a research project I can have the department handle the expense, but that doesn't feel quite right, and I doubt they will put up with this nonsense for long. There is a CERDIP version of the chip which I'd very much like to obtain, but I checked Mouser, Newark, LCSC, Arrow electronics, and Digikey and none have the part in stock. If anyone here can help me find one of these I would greatly appreciate it. If not I will need to find a suitable replacement, preferably something that wont involve rewriting all my code. As of now I'm using the UART and SPI interface, so at the very least I'll need a part that has those two functions.

author: oPossum
author_rank: Super Contributor
timestamp: October 12, 2019, 09:19:59 pm
content: https://www.microchip.com/wwwproducts/en/PIC16F74

author: 1Ghz
author_rank: Unknown
timestamp: October 12, 2019, 09:27:51 pm
content: https://www.microchip.com/wwwproducts/en/PIC16F747(compatible with the PIC16C7x devices, more interrupts, better ADC, more CCP, in-circuit debugger)https://www.microchip.com/wwwproducts/en/PIC16F874(compatible with the PIC16C7x devices, more interrupts, better ADC, data EEPROM, in-circuit debugger, low-voltage programming)https://www.microchip.com/wwwproducts/en/PIC16F874A(compatible with the PIC16C7x devices, more interrupts, better ADC, data EEPROM, in-circuit debugger, low-voltage programming + analog comparators)https://www.microchip.com/wwwproducts/en/PIC16F884(newer device, Enhanced CCP, more ADC channels, etc...)

author: TomS_
author_rank: Frequent Contributor
timestamp: October 13, 2019, 08:42:35 am
content: Quote from: Dukov Ahzrukhal on October 12, 2019, 08:59:18 pmWhat caused you to choose this part?

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: October 13, 2019, 09:08:45 am
content: Use the 16f874 instead- flash memory, otherwise pretty much identical. There is no reason to use ancient parts like the 16c seris

author: voltsandjolts
author_rank: Unknown
timestamp: October 13, 2019, 09:32:28 am
content: Quote from: mikeselectricstuff on October 13, 2019, 09:08:45 amUnless the OP's application requires the hermetically sealed die offered by the CERDIP package.Very likely it doesn't.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 13, 2019, 10:38:30 am
content: Heh, I inherited a handful of vintage (late 90s) PICs in CERDIP, but they're the -72 and -73. Rats.Tim

author: Dukov Ahzrukhal
author_rank: Regular Contributor
timestamp: October 13, 2019, 01:56:49 pm
content: Whats wrong with the 16C series? I know its old, but the plastic versions are still available. I suppose I can use any other part, I mostly stick to these so I can reuse some of the subroutines I've already written. I've used the PIC16F84A in the past, but that one is also pretty old and doesn't have SPI or a UART.

author: hexreader
author_rank: Frequent Contributor
timestamp: October 13, 2019, 02:50:28 pm
content: Quote from: Dukov Ahzrukhal on October 13, 2019, 01:56:49 pmIt is only programmable one time, and support (such as windowed CERDIP) is hard to findFine for production, but not good for development.You starting this thread is evidence of the problem with OTP parts... in a nutshell - cost, time and inconvenience when developing.

author: TomS_
author_rank: Frequent Contributor
timestamp: October 13, 2019, 02:53:24 pm
content: Quote from: Dukov Ahzrukhal on October 13, 2019, 01:56:49 pmWell, as you are finding, they are only one time programmable, which makes debugging difficult and expensive. You're going to burn through a lot of them before you get stable code.The CERDIP parts are likely the same basic die, but with the window so they can be erased and reprogrammed during development. You could use these, but why? You can still only program them once and then need to erase then the same way you do an EPROM - with a UV eraser. You'll have to keep swapping them in and out of the circuit to do that. With a flash based part you can do this in-circuit within seconds using something like a PICKIT or ICD. As for debugging, you can set breakpoints and check memory contents, single step etc to see what your code is doing and then make fixes before reprogramming.Other than that they are just old tech. You can get modern parts with more and better peripherals and other features. If your application has no legacy, there's simply no point using these old parts.

author: PCB.Wiz
author_rank: Super Contributor
timestamp: October 14, 2019, 01:18:43 am
content: Quote from: Dukov Ahzrukhal on October 13, 2019, 01:56:49 pmThe main 'avoid' flag is theOTP, I am sure there areFLASHPIC's that can run subroutines you have already written.

author: Dukov Ahzrukhal
author_rank: Regular Contributor
timestamp: October 14, 2019, 08:24:51 pm
content: I do realize that these old parts are inconvenient when it comes to debugging. For now I will use the PIC16C65 because it has all I need and I found a bunch in CERDIP package, but I will avoid using them for my future projects. Part of the reason why I have not tried using more modern parts is that most have a million features that I don't need, so reading through the datasheet can get very tedious. The PIC16F747 seems like a good alternative though.

author: jaromir
author_rank: Unknown
timestamp: October 15, 2019, 05:25:38 am
content: PIC16F74 is as close to 16C74 as it gets. It has the same peripherals - 3xTimer, capture/compare/PWM, SSP, AD, UART - the same pinout, the same instruction set, the same memory layout.Different is programming method (fortunately) and somehow different is configuration word.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: October 15, 2019, 09:29:12 am
content: Quote from: Dukov Ahzrukhal on October 14, 2019, 08:24:51 pmIn most cases you can ignore the extra features - they are disabled by default. The only exception is analogue pins, which need to be disabled for them to work as digital inputs by clearing the ANSELx register(s).You are wasting a lot of your time messing about with EPROM parts. Let me guess, you're still writing in assembler too?

author: wraper
author_rank: Unknown
timestamp: October 15, 2019, 09:30:35 am
content: Quote from: mikeselectricstuff on October 15, 2019, 09:29:12 amAnd money by paying way more for inferior legacy ICs.