ST9 Extended Addressing Mode

[johanpauvert2]

Posted on January 16, 2003 at 09:34

ST9 Extended Addressing Mode

[johanpauvert2]

Posted on May 17, 2011 at 11:33

I am confused with the ST9 capability regarding external memory addressing. Can anyone clarify how much memory we can address using a ST90158, ST92F124 or ST92F120 ?

Skywalker

[johan239955_stm1_stmicro]

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