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C166 question about memory

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whoops

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Any C166 users out here who knows the answer ?
When the C166 is used with byte wide memories a WRH and WRL signal need to be used to write only to one chip when byte accesses are made.
BUT what if a 16 bit wide memory is connected to the cpu ?? In case of a byte write 2 bytes are written at a time, so I don`t understand why here the problem does not happen.
Is it connect that in case of a 16bit mem device A0 of the mem has to be connected t0 A1 of the 166 ?

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Please don't reply unless you have useful information to add on this post.Thanks
 

quacklamack

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If you are connecting a 16 bit memory to the C167, you must indeed connect memory A0 to chip A1, since the memory is 2 bytes wide. Then, the WRH/WRL pin has no use in bus management and may be therefore used in other applications.

I was quite confused on your question, but I think this provides an answer, does it not?

Quack
 

woodooman

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Hi, did you read "The Insider's Guide To Planning 166 Family Designs" from Hitex??? I don't know, but maybe it helps you. This stuff is downloadable from web for free.

Bye. WDM
 

GeneralMadDog

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Hi whoops,

in it's default configuration, a C16x uses only one WR signal for 16Bit Memory. With a pull down resistor on P0H.0 you can change the write configuration at startup. Then WR becomes WRL for the lower byte and BHE becomes WRH for the upper byte. In a 8bit/16bit mixed design you must connect WRL to a 16bit device (e.g. 16bit flash).
And you should follow the tip of woodooman, "The Insider's Guide To Planning 166 Family Designs" is a very good refernce for C16x designs.

Bye
The General
 

quacklamack

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Actually, you may find valuable having the WRH connectted to the WR pin of the upper 8bit memory chip, and the WRL to the other, since an 8 bit transfer would have to read the existing word in order to write it again. Nevertheless, most of the present-day compilers count on that and transfer mostly 16 bit words (they mirror memory on registers by two bytes), but an assembler programmer could certyaily make user of it on 8-bit parted registers (like writing P0L and P0H or P8 to memory).

Quack
 

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