[Coco] Fest Weekend

jdaggett at gate.net jdaggett at gate.net
Thu Apr 5 17:36:48 EDT 2007

On 5 Apr 2007 at 5:51, coco at yourdvd.net wrote:

> I found out my CoCo didn't like an
> 'HC245' but it could digest the 'F245 and 'LS245 (original part) - so
> by next visitation, we were ready to kill some more evil space drones
> :-)

HCMOS devices are not guaranteed to be compatible with LS TTL devices or 
NMOS devices. The MC6809E is NMOS and can drive one TTL load. There is a 
range of about 0.7 VDC that there can be an incompatiblity. Vinput high for the H 
C245 is 3.15VDC. The minimum Voutput high for the MC68B09E is 2.4VDC. If 
the MC6809E is loaded enough, the HC245 will never see a logic "1" at the 
inputs. LSTTL and Fast TTL logic will work. ALso HCT logic will work with NMOS 

Also TTL/LSTTL  have higher noise immunity than HCMOS and CMOS logic. 


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