cmos vs ttl logic in schematics design

[Altera_Forum]

Hi, 

I am designing cyclone 3 FPGA board in which i have come across cmos logic circuit and ttl logic circuit.  can i connect 3.3v of both the cmos and ttl logic? what are all the things we have to taken care when go for different logics? Thanx in advance :)  Regards, Shahul

[Altera_Forum]

--- Quote Start ---  Hi, what are all the things we have to taken care when go for different logics? Shahul  --- Quote End ---   http://focus.ti.com/lit/sg/sdyu001z/sdyu001z.pdf page 9.

[Altera_Forum]

A 3.3V I/O standard can drive LVTTL, LVCMOS(both 3.3V supply) and TTL (5V supply). To drive 5V CMOS (e.g. 74HC family), you need a level converter. 74HCT logic has TTL levels on input and can be driven by the 3.3V I/O. 

 5V logic must not drive the FPGA without level conversion or voltage clamping.

[Altera_Forum]

thanx for ur reply 

It will be useful.   Regards, shahul