CPLDs are not a cheap way to add lots of pins.=20
the reason is silicon area - lots of pins =3D more space needed around
the edge of die =3D bigger die =3D fewer chips made per wafer =3D more
expensive chips.=20
This is the reason you never see chips with lots of pins but not so
many gates - as the chip has to be big to accommodate the pins, the
internal die area adds no cost, so they fill it up with gates or
whatever.=20




On Thu, 20 Jun 2002 07:43:18 -0700, you wrote:

>Thanks Al. I will take a look at the tuturial.
>
>What is the estimated cost per output 100 pin when using CPLD ?
>
>(assuming large quantities and surface mount)
>
>Thanks,
>
>Tal
>
>> -----Original Message-----
>> From: pic microcontroller discussion list
>> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Al Williams
>> Sent: Thursday, June 20, 2002 6:14 AM
>> To: PICLIST@MITVMA.MIT.EDU
>> Subject: Re: [PIC]: cheapest way for adding output pins ?
>>
>>
>> Consider using a CPLD device. I have a tutorial for the Xilinx CPLDs
>> that includes a project that hooks up (I think) 32 I/O to a Basic =
Stamp.
>> The design could easily be expanded to handle more pins in a 95108
>> device. Two of these would get you there. We don't sell the expander =
per
>> se as a product, but our Xilinx prototyping boards are great for =
getting
>> started with this type of technology.
>>
>> The other alternative, since you only need outputs, is a shift =
register,
>> but that is a whopping number of packages. The device in the tutorial =
is
>> really just a way to gang a bunch of shift registers, but they are all
>> in one semi-custom chip (and they are fairly cheap). With a CPLD in =
PLCC
>> packaging you'd need two. If you were willing to go with surface mount
>> (like a TQFP package) you could do it in one package plus have enough
>> spare to do some other things if you wanted to.
>>
>> The tutorials (along with an Altera and PIC tutorial) are at
>> http://www.al-williams.com/pictutor
>>
>> Good luck!
>>
>> Al Williams
>> AWC
>> * Easy RS-232 Prototyping
>> http://www.al-williams.com/awce/rs1.htm
>>
>>
>>
>> > -----Original Message-----
>> > From: pic microcontroller discussion list
>> > [mailto:PICLIST@MITVMA.MIT.EDU] On Behalf Of Tal Dayan
>> > Sent: Wednesday, June 19, 2002 11:18 PM
>> > To: PICLIST@MITVMA.MIT.EDU
>> > Subject: [PIC]: cheapest way for adding output pins ?
>> >
>> >
>> > Hello,
>> >
>> > One of the designs I am working needs many (100 to 200)
>> > outputs pins (0/5V
>> > signal) controlled by a single mid size PIC. What is the
>> > cheapest way (cents per output pin) adding output pins to a PIC ?
>> >
>> > This is a mass production product but an ASIC is out of
>> > question at this point.
>> >
>> > Speed is not an a primary issue so using reasonable serial
>> > communication is OK.
>> >
>> > Thanks,
>> >
>> > Tal
>> >
>> > --
>> > http://www.piclist.com hint: To leave the PICList
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>> >
>>
>> --
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>>

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