Extended Instruction Set Affecting Standard Instructions?

(instructions, reset, WDT, specifications...) PIC17Cxx, PIC18Fxxx

Extended Instruction Set Affecting Standard Instructions?

Postby Joseph Watson » Tue Oct 13, 2015 6:36 am

I am currently using the PIC18F4620 in assembly language but this question would likely pertain to most of the PIC18F series chips. I see that the Extended Instruction Set can be enabled by an appropriate CONFIG setting. I understand that the Extended Instruction Set was included primarily for the benefit of high level language compilers such as C, but clearly if one wants to have subroutines that allocate storage in a software stack, it could also have benefits for someone working in assembly.

If one enables the Extended Instruction Set, does it alter how some of the Standard Instruction Set instructions behave? I don't yet see where the data sheet says that it changes the way any standard instructions behave but one would think if it does not affect the standard instructions, there would be no reason to ever disable the Extended Instruction Set. Does anyone have a good handle on this? Why is it optional?

Thanks,
Joe
NCR once refused to hire me because I was too short. I'm still waiting on my growth spurt.
User avatar
Joseph Watson
 
Posts: 49
Joined: Sat May 31, 2014 8:06 pm
Location: Ohio, USA
PIC experience: Experienced Hobbyist

Re: Extended Instruction Set Affecting Standard Instructions

Postby ric » Tue Oct 13, 2015 11:12 am

I don't know the details, but it must have some effect, because the XC8 compiler falls over if you enable it.
Latest test project, an LED matrix display made from one reel of addressable LEDs. here
User avatar
ric
Verified identity
 
Posts: 659
Joined: Sat May 24, 2014 2:35 pm
Location: Melbourne, Australia
PIC experience: Professional 5+ years with MCHP products

Re: Extended Instruction Set Affecting Standard Instructions

Postby vloki » Tue Oct 13, 2015 12:00 pm

There was a funny discussion in MCHP forum -> http://www.microchip.com/forums/FindPost/632427
vloki
Verified identity
 
Posts: 186
Joined: Wed May 28, 2014 8:42 am
Location: Germany
PIC experience: Professional 5+ years with MCHP products

Re: Extended Instruction Set Affecting Standard Instructions

Postby Entropy » Tue Oct 13, 2015 12:17 pm

vloki wrote:There was a funny discussion in MCHP forum -> http://www.microchip.com/forums/FindPost/632427

how do you remember a 3 year old discussion forum post? :shock:
Entropy
 
Posts: 24
Joined: Fri Sep 04, 2015 7:04 am
Location: Timisoara, Romania

Re: Extended Instruction Set Affecting Standard Instructions

Postby ric » Tue Oct 13, 2015 12:42 pm

It was an epic one. I remember it too. :)
Latest test project, an LED matrix display made from one reel of addressable LEDs. here
User avatar
ric
Verified identity
 
Posts: 659
Joined: Sat May 24, 2014 2:35 pm
Location: Melbourne, Australia
PIC experience: Professional 5+ years with MCHP products

Re: Extended Instruction Set Affecting Standard Instructions

Postby Joseph Watson » Tue Oct 13, 2015 4:00 pm

Previously, I wrote:
I don't yet see where the data sheet says that it changes the way any standard instructions behave ....
:oops:

Please excuse the questionable eyesight and the lack of persistence in this old guy trying to read the data sheet. Your response was very helpful indeed.

Thanks again,
Joe
NCR once refused to hire me because I was too short. I'm still waiting on my growth spurt.
User avatar
Joseph Watson
 
Posts: 49
Joined: Sat May 31, 2014 8:06 pm
Location: Ohio, USA
PIC experience: Experienced Hobbyist

Re: Extended Instruction Set Affecting Standard Instructions

Postby jtemples » Tue Oct 13, 2015 6:44 pm

You lose most or all of your access RAM when it's enabled. That's the downside.
jtemples
Verified identity
 
Posts: 195
Joined: Sun May 25, 2014 2:23 am
Location: The 805
PIC experience: Professional 5+ years with MCHP products


Return to 16-Bit Core

Who is online

Users browsing this forum: No registered users and 9 guests

cron