replacing 74LS with 74HCT

[Active8]

hi:

microchip an589 - the in circuit programmer... it uses a 74LS244 tri-
state octal line driver between the computer's LPT port and the PIC.

i only found it in one catalog and got to thinking that HCT might be the
way to go since i can find it faster in more places. HCT not HC since
IIRC the LPT port is TTL level, eh?

can anyone give me a reason why this would be a bad or not so good
thing? *i* can't think of anything other than noise margin - don't know
if the HCT is the same in that respect, but i'm lookin'. no hysteresis
symbol, but it says it's a drop-in replacement. i don't expect a bunch
of noise - it's all being absorbed by my line level speaker wires which
run near the monitor cable

anything else?

TIA,
mike

 

[Paul Burke]

hi:

microchip an589 - the in circuit programmer... it uses a 74LS244 tri-
state octal line driver between the computer's LPT port and the PIC.

i only found it in one catalog and got to thinking that HCT might be the
way to go since i can find it faster in more places. HCT not HC since
IIRC the LPT port is TTL level, eh?

It's a while since I looked at the TTL books but IIRC the LS has a
little hysteresis on the inputs which the HCT doesn't have. I doubt if
it matters. Whatthehell, it's only about 25p for the HCT part, suck it
and see!

Make sure any unused inputs are pulled somewhere sensible, that's all.

Paul Burke

 

[Active8]

It's a while since I looked at the TTL books but IIRC the LS has a
little hysteresis on the inputs which the HCT doesn't have.

right. like i said, i'm not expecting much noise.

I doubt if
it matters. Whatthehell, it's only about 25p for the HCT part, suck it
and see!

yeah, order a couple of each just in case and hope the LS chips stay
around. i hate ordering parts.

brs,
mike

 

[Byron A Jeff]

-
-microchip an589 - the in circuit programmer... it uses a 74LS244 tri-
-state octal line driver between the computer's LPT port and the PIC.

Quite similar to my Trivial programmers located here:

http://www.finitesite.com/d3jsys

-
-i only found it in one catalog and got to thinking that HCT might be the
-way to go since i can find it faster in more places. HCT not HC since
-IIRC the LPT port is TTL level, eh?

Correct. In fact the LS really isn't a good part for the job because it doesn't
gurantee outputs above 4.0V for a 5V Vdd.

-
-can anyone give me a reason why this would be a bad or not so good
-thing?

Quite the opposite. As I point out on my TLVP page, HCT parts are required
for parallel ports that meet the TTL requirement, but only output 3.3V.

- *i* can't think of anything other than noise margin - don't know
-if the HCT is the same in that respect, but i'm lookin'. no hysteresis
-symbol, but it says it's a drop-in replacement. i don't expect a bunch
-of noise - it's all being absorbed by my line level speaker wires which
-run near the monitor cable

Go ahead and do it. BTW if you haven't built it yet and you are programming
Flash parts, you may want to check out my Trivial High Voltage programmer,
which has a slightly simpler schematic.

-
-anything else?

One last thing. AN589 has the same lack of termination as my Trivial
Programmers. So be sure to use a short cable to connect to the parallel port.

BAJ

 

[Active8]

-
-microchip an589 - the in circuit programmer... it uses a 74LS244 tri-
-state octal line driver between the computer's LPT port and the PIC.

Quite similar to my Trivial programmers located here:

http://www.finitesite.com/d3jsys

that's worth a shot maybe. before i head down the rabbit trail... is the
Tait SW you recommend going be as good as the IC-prog sw? IC-Prog will
verify as it goes so the protect bit gets set last and optionally just
program the config after the codes loaded and verified? it's a nice
program IMHO. no details on the Tait app.

-
-i only found it in one catalog and got to thinking that HCT might be the
-way to go since i can find it faster in more places. HCT not HC since
-IIRC the LPT port is TTL level, eh?

Correct. In fact the LS really isn't a good part for the job because it doesn't
gurantee outputs above 4.0V for a 5V Vdd.

and at 5V Vdd, that's pushing the worst case of some of the PIC inputs.
so much for their ANs. gotta watch it.

-
-can anyone give me a reason why this would be a bad or not so good
-thing?

Quite the opposite. As I point out on my TLVP page, HCT parts are required
for parallel ports that meet the TTL requirement, but only output 3.3V.

there we go! IIRC laptops'll do that.

- *i* can't think of anything other than noise margin - don't know
-if the HCT is the same in that respect, but i'm lookin'. no hysteresis
-symbol, but it says it's a drop-in replacement. i don't expect a bunch
-of noise - it's all being absorbed by my line level speaker wires which
-run near the monitor cable

Go ahead and do it.

if you mean use LS, forget it. it's too marginal. i think you mean use
HCT.

BTW if you haven't built it yet and you are programming
Flash parts, you may want to check out my Trivial High Voltage programmer,
which has a slightly simpler schematic.

always looking for a bit here, a bit there. i'll be adding improvements
to whatever i do, eventually. right now it's a quickie that'll work with
the IC-Prog software - unless that Tait prog is worthwhile. most i'll do
above and beyond for now is test over different Vdds.

-
-anything else?

One last thing. AN589 has the same lack of termination as my Trivial
Programmers. So be sure to use a short cable to connect to the parallel port.

gotcha. thanks a boatload.

brs,
mike

 

[Wouter van Ooijen]

microchip an589 - the in circuit programmer... it uses a 74LS244 tri-

state octal line driver between the computer's LPT port and the PIC.

If you want to go this route prepare for some trouble - I have hear of
people who could not get this type of programmer to work, even with a
design that worked perfectly for other people. Issues with port output
levels, cable length and a zillion other minor but fatal details. And
for NT-derived windoze you will need direct-port-access-drivers, and
the whole process will be quite slow.

For the newer PICs that have LVP you might want to google for the
'trivial LVP programmer'. Or go the safe route, for instance with my
Wisp628


Wouter van Ooijen

-- ------------------------------------
http://www.voti.nl
PICmicro chips, programmers, consulting

 

[Byron A Jeff]

-In article <[email protected]>, [email protected] says...
-> In article <[email protected]>,
-> -hi:
-> -
-> -microchip an589 - the in circuit programmer... it uses a 74LS244 tri-
-> -state octal line driver between the computer's LPT port and the PIC.
->
-> Quite similar to my Trivial programmers located here:
->
-> http://www.finitesite.com/d3jsys
-
-that's worth a shot maybe. before i head down the rabbit trail... is the
-Tait SW you recommend going be as good as the IC-prog sw? IC-Prog will
-verify as it goes so the protect bit gets set last and optionally just
-program the config after the codes loaded and verified? it's a nice
-program IMHO. no details on the Tait app.

The Trivial serial ends up being a Tait style programmer. So if IC-prog
works with Tait style programmers, then there should be no problem.

I haven't seen any reports in the TLVP forum indicating that IC-Prog works
or not.

->
-> -
-> -i only found it in one catalog and got to thinking that HCT might be the
-> -way to go since i can find it faster in more places. HCT not HC since
-> -IIRC the LPT port is TTL level, eh?
->
-> Correct. In fact the LS really isn't a good part for the job because it doesn't
-> gurantee outputs above 4.0V for a 5V Vdd.
-
-and at 5V Vdd, that's pushing the worst case of some of the PIC inputs.
-so much for their ANs. gotta watch it.
->
-> -
-> -can anyone give me a reason why this would be a bad or not so good
-> -thing?
->
-> Quite the opposite. As I point out on my TLVP page, HCT parts are required
-> for parallel ports that meet the TTL requirement, but only output 3.3V.
-
-there we go! IIRC laptops'll do that.

That's where the HCT part in the TLVP comes from. Failure on a straight cable
on a 3.3V parallel port.

->
-> - *i* can't think of anything other than noise margin - don't know
-> -if the HCT is the same in that respect, but i'm lookin'. no hysteresis
-> -symbol, but it says it's a drop-in replacement. i don't expect a bunch
-> -of noise - it's all being absorbed by my line level speaker wires which
-> -run near the monitor cable
->
-> Go ahead and do it.
-
-if you mean use LS, forget it. it's too marginal. i think you mean use
-HCT.

Yes I meant HCT.

-
-> BTW if you haven't built it yet and you are programming
-> Flash parts, you may want to check out my Trivial High Voltage programmer,
-> which has a slightly simpler schematic.
-
-always looking for a bit here, a bit there. i'll be adding improvements
-to whatever i do, eventually. right now it's a quickie that'll work with
-the IC-Prog software - unless that Tait prog is worthwhile. most i'll do
-above and beyond for now is test over different Vdds.

Cool.

-> -
-> -anything else?
->
-> One last thing. AN589 has the same lack of termination as my Trivial
-> Programmers. So be sure to use a short cable to connect to the parallel port.
-
-gotcha. thanks a boatload.

No problem,

BAJ

 

[Active8]

for NT-derived windoze you will need direct-port-access-drivers, and
the whole process will be quite slow.

i have the driver, but...

For the newer PICs that have LVP you might want to google for the
'trivial LVP programmer'. Or go the safe route, for instance with my
Wisp628

i have your page open. i might make a Wisp628 after i have a programmer.
i'm bootstrapping my tool set. IOW, i have to be able to burn a PIC to
make a Wisp628. i'll most likely take the best of the best and add my
own stuff. maybe there'll be a Wisp of the Wisp628 in there should
be WISP or W.I.S.P., but Wisp looks better.

i came back here to get the link to the trivial programmer, above in
thread. i didn't know you were here. my alert rules are sleeping again


thanks,
mike

 

[Active8]

-> Quite similar to my Trivial programmers located here:
->
-> http://www.finitesite.com/d3jsys

gotta thank you again. your info on the 16F628... that chip is sweet. i
wouldn't have thought to look at higher numbers while trying to keep the
price down.

tnx,
mike

 

[Byron A Jeff]

-> -> Quite similar to my Trivial programmers located here:
-> ->
-> -> http://www.finitesite.com/d3jsys
->
->
-gotta thank you again. your info on the 16F628... that chip is sweet. i
-wouldn't have thought to look at higher numbers while trying to keep the
-price down.

No problem. Glad to help.

The two must check out parts are the 16F819 and the 16F88.

If a hardware USART isn't critical then you must check out the 16F819. 3 timers
CCP, I2C/SPI, and can write its own program memory, so it's bootloadable.
Absolutely amazing. I just wish it had a hardware USART because it would be
the only 18 pin PIC part I'd ever use.

Now the 16F88 actually has it all including the hardware USART and twice the
memory of the 16F819. In fact I'm so impressed with it that I think I'll go
ask Microchip for a few samples and get it working with TLVP programmer.

BAJ

 

[Active8]

The two must check out parts are the 16F819 and the 16F88.

If a hardware USART isn't critical then you must check out the 16F819. 3 timers
CCP, I2C/SPI, and can write its own program memory, so it's bootloadable.
Absolutely amazing. I just wish it had a hardware USART because it would be
the only 18 pin PIC part I'd ever use.

Now the 16F88 actually has it all including the hardware USART and twice the
memory of the 16F819. In fact I'm so impressed with it that I think I'll go
ask Microchip for a few samples and get it working with TLVP programmer.

BAJ

i take it that the 'F88 isn't bootloadable then or you'd have no need to
mention your wishes for the 'F819.

or maybe the 'F88 has more pins.

i'm filing all this good info, BTW. it'll save time later.

brs,
mike

 

[Byron A Jeff]

-<snip>
-> The two must check out parts are the 16F819 and the 16F88.
->
-> If a hardware USART isn't critical then you must check out the 16F819. 3 timers
-> CCP, I2C/SPI, and can write its own program memory, so it's bootloadable.
-> Absolutely amazing. I just wish it had a hardware USART because it would be
-> the only 18 pin PIC part I'd ever use.
->
-> Now the 16F88 actually has it all including the hardware USART and twice the
-> memory of the 16F819. In fact I'm so impressed with it that I think I'll go
-> ask Microchip for a few samples and get it working with TLVP programmer.
->
-> BAJ
->
-i take it that the 'F88 isn't bootloadable then or you'd have no need to
-mention your wishes for the 'F819.

Yes it is. I just started writing on the 819 first and then went back and
checked the specs on the '88. You can buy both parts with cheap shipping from
Randy Jones at http://www.glitchbuster.com or if you're willing to wait
a few days you can sample from Microchip directly.

-
-or maybe the 'F88 has more pins.

Nope. All of these are 18 pin parts.

BAJ

 

[Active8]

Yes it is. I just started writing on the 819 first and then went back and
checked the specs on the '88. You can buy both parts with cheap shipping from
Randy Jones at http://www.glitchbuster.com or if you're willing to wait
a few days you can sample from Microchip directly.

-
-or maybe the 'F88 has more pins.

Nope. All of these are 18 pin parts.

then this is too cool.

uChip site is throwing an error on "buy" option and i'm saving my sample
limit for some rfPICs. i'm wondering what the advantage(s) is(are) to
buying from Glitchbuster as opposed to directly from uChip and whether
uChip's 5 sample limit is per request or per human life span

couple/5 years ago, i got into programming PICs but never went any
further. now it's time to get moving. after these 2 projects i'm doing
are complete, i think i'll do a GP developement system, maybe. i don't
know. i'll have to look at the capabilities of the ready made "labs" i
see from time to time.

i didn't notice if you have a mailing list, but i'd not be opposed to
hearing about future additions to your site.

brs,
mike

 

[Wouter van Ooijen]

i have your page open. i might make a Wisp628 after i have a programmer.

i'm bootstrapping my tool set. IOW, i have to be able to burn a PIC to
make a Wisp628. i'll most likely take the best of the best and add my
own stuff. maybe there'll be a Wisp of the Wisp628 in there should
be WISP or W.I.S.P., but Wisp looks better.

1. You could use an almost-no-parts serial port programmer. They can
be a bit unreliable, but maybe good enough for programming a PIC once
2. If you can't program your own (and don't want to buy the kit) I
sell pre-programmed 16F628's


Wouter van Ooijen

-- ------------------------------------
http://www.voti.nl
PICmicro chips, programmers, consulting

 

[Active8]

1. You could use an almost-no-parts serial port programmer. They can
be a bit unreliable, but maybe good enough for programming a PIC once
2. If you can't program your own (and don't want to buy the kit) I
sell pre-programmed 16F628's

thanks. i like doing stuff myself exactly the way i want it. like i
said, the best of the best plus. no room for unreliable no parts
programmers, either. i build things to work, not things to work on

no worries mate, as soon as the chips get here, i *will* have a
programmer. i've got buffers and all on hand, just need the PICs.

but i hate trying to get an order together that covers everything so i
don't have to do it again. i'm working on two other projects. i really
miss bainsville electronics in baltimore.

brs,
mikw