74hc and 74ls interchang able ?
 

hi, i`m trying to build a bdm32 interface to program my saab trionic ecu ,
put the parts list is for hc ttl ic`s , i have ls ttl ic`s , are these
interchangable ?
thanks,
mark k

74hc and 74ls interchang able ?
 

The threshold voltages are a bit different but otherwise, they are roughly
equivalent. Where things fall apart is when you try to kluge a digital part
for an analog function. There they have big differences.

"mark krawczuk" wrote in message
...
hi, i`m trying to build a bdm32 interface to program my saab trionic ecu
, put the parts list is for hc ttl ic`s , i have ls ttl ic`s , are these
interchangable ?
thanks,
mark k

74hc and 74ls interchang able ?
 

"mark krawczuk" wrote in message
...
hi, i`m trying to build a bdm32 interface to program my saab trionic ecu
, put the parts list is for hc ttl ic`s , i have ls ttl ic`s , are these
interchangable ?
thanks,
mark k

Sometimes....... If your interface and drive to the saab unit is 5V, then
probably....... if it's 5V then definitely no.

74hc and 74ls interchang able ?
 

TT_Man wrote:
"mark krawczuk" wrote in message
...
hi, i`m trying to build a bdm32 interface to program my saab trionic ecu
, put the parts list is for hc ttl ic`s , i have ls ttl ic`s , are these
interchangable ?
thanks,
mark k

Sometimes....... If your interface and drive to the saab unit is 5V, then
probably....... if it's 5V then definitely no.


and some extra pull-up resistors on ls out to cmos in does
not hurt either.

74hc and 74ls interchang able ?
 

mark krawczuk wrote:

hi, i`m trying to build a bdm32 interface to program my saab trionic ecu ,
put the parts list is for hc ttl ic`s , i have ls ttl ic`s , are these
interchangable ?

Certainly not 100% reliably.

Graham

74hc and 74ls interchang able ?
 

Sjouke Burry wrote:

TT_Man wrote:
"mark krawczuk" wrote in message
...
hi, i`m trying to build a bdm32 interface to program my saab trionic ecu
, put the parts list is for hc ttl ic`s , i have ls ttl ic`s , are these
interchangable ?
thanks,
mark k

Sometimes....... If your interface and drive to the saab unit is 5V, then
probably....... if it's 5V then definitely no.


and some extra pull-up resistors on ls out to cmos in does
not hurt either.

That does certainly help.

Graham

74hc and 74ls interchang able ?
 

On Thu, 31 Jul 2008 15:02:57 +0930, "mark krawczuk"
wrote:

hi, i`m trying to build a bdm32 interface to program my saab trionic ecu ,
put the parts list is for hc ttl ic`s , i have ls ttl ic`s , are these
interchangable ?
thanks,

I believe AC and AHC were developed to be more TTL compatible. The
problem is input logic level recognition.

RL

74hc and 74ls interchang able ?
 

On Fri, 01 Aug 2008 11:29:26 -0400, legg wrote:

On Thu, 31 Jul 2008 15:02:57 +0930, "mark krawczuk"
wrote:

hi, i`m trying to build a bdm32 interface to program my saab trionic ecu ,
put the parts list is for hc ttl ic`s , i have ls ttl ic`s , are these
interchangable ?
thanks,

I believe AC and AHC were developed to be more TTL compatible. The
problem is input logic level recognition.

---
That's true on the CMOS side, but I think AC and AHC were developed
for higher speeds than available in HC and HCT, HCT and ACT being
developed to allow compatibility with bipolar TTL outputs.

TI recommends a pullup to Vcc on the TTL part to remove the
incompatibility, with a value of:


Vcc - TTL Vol(max)
R = ---------------------
TTL Iol + n CMOS Il


JF