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#1
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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 |
#2
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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 news 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 |
#3
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74hc and 74ls interchang able ?
"mark krawczuk" wrote in message news 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. |
#4
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74hc and 74ls interchang able ?
TT_Man wrote:
"mark krawczuk" wrote in message news 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. |
#5
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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 |
#6
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74hc and 74ls interchang able ?
Sjouke Burry wrote: TT_Man wrote: "mark krawczuk" wrote in message news 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 |
#7
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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 |
#8
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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 |
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