Posted on May 17, 2011 at 11:33 Thanks to the MMU, the ST9 has an 4M addressing space (4M = 22-bit addresses)
However, some ST9 versions do not have all external address pins bounded on a given package. For instance, the ST92F124 TQFP64 only has a 16-bit external memory bus when its PQFP100 has all 22-bit pins bounded.
Anyway, there is an application note available on this web site to overcome this limitation : check AN 1069, ''addressing up to 4M bytes of memory from a ST9+ with a 16-bit external bus''.
As summary, this is what you have :
- ST90158 ROM and OTP
Only 16-bit address bus available on the chip however thanks to AN1069, maximum accessible memory is then ~3.9M.
- ST90R158 ROMless
Only 16-bit address bus available on the chip however thanks to AN1069, maximum accessible memory is then ~1.9M
- ST92F120
Only 16-bit address bus available on the chip. Also, segment 2 and 3 are the only external segment user accessible which means the maximum accessible memory is then ~260k
- ST92124, F124, 150, F150 and F250
TQFP100 and PQFP100 versions : the 22-bit address bus allows to address 4M of external and internal memory
TQFP64 versions : only 16-bit address bus bounded on the chip however thanks to AN1069 maximum accessible memory is then ~3.9M.
Jojo
