external RAM: 16Bit-Write-Access dont work

siegmund · ‎2004-05-17

Posted on May 18, 2004 at 04:53

siegmund · ‎2011-05-17

Posted on May 17, 2011 at 11:35

hello all,

i have connected external RAM to the ST92F150CV as shown in Figure 74 in Datasheet V1.5 (MC=0).

nearly everything works, even programm-execution, but 16bit-write-access doesnt work.

the logic-analyzer shows, that signal E/ (from ST9::A21) and signal W/ (from ST9::RW\) dont change beetween both 8bit accesses.

but the RAM needs a change, either the E/ or W/.

what is wrong?

thanks a lot!

attached: picture from analyzer, shows first 8bit-write access and later 16bit-write-access (programm-execution from same RAM)

[ This message was edited by: siggi on 04-03-2004 13:51 ]

kapil · ‎2011-05-17

Posted on May 17, 2011 at 11:35

you can refer to AN1076 and AN1069, for external memory interface.

link is

http://cmg.st.com/stonline/products/cmg/mcd/familiesdocs.php?FAM=16

siegmund · ‎2011-05-17

Posted on May 17, 2011 at 11:35

hi chaps,

thanks for the application notes.

everything seems to be all right.

program-execution and 8bit read-write-accesses are working, even 16bit read-accesses.

only 16bit-write wont work.

any other hint?

thanks.

ritu · ‎2011-05-17

Posted on May 17, 2011 at 11:35

Hello Siggi,

If you are using external memory interface in mc = 0 mode. Both the signals /E and /rw should maintain the same value during the whole wirte or read cycle. (Both /rw and chip select should stay at low level in case of write cycle.) I wonder if you see any change in these signals during 8 bit write access ??

Also there seems to be some incohrence b/w the the signals shown in pic and their actual behaviour in mc=0 mode. First of all the name of the signals are different from mc= 0 mode (WEN in place of /rw and /OEN in place of /DSN). Also /WEN (/rw) signal should maintain the same value for the whole read/write access. (In case of mc =0) The one shown in the pic seems to be for mc=1.

Rds,

Ritu