Maybe I haven't had my coffee this morning. But I'm hung up on something in the Semper address space mapping.
I know that when a page is accessed two 32 byte half pages are accessed. And I'm aware that Semper uses "mirror bit" technology.
But I see a 2x issue with respect to the number of byte addresses in a sector and the size of the sector. I'm trying to understand what basic thing I'm overlooking.
Likely it's something obvious.
In the image below we have a 128KB sector with only 16 bits of address space... last I googled 16 bits define a 64K address space
By the same token a Uniform Sector layout of 256K byte sectors has an address range of 0x0-0x1FFFF (17 bits) which defines a 128K Addressing range not a 256K addressing range. I re read the documentation multiple times, but I can't figure out how to access 256K of unique bytes with only 128K of address space.
What big thing am I missing?
I'm looking at Document Number 002-12337 Rev O. Specifically the 256KB UniformSectorAddressMap.
What is it about SemperMirror Bit technology that I am missing where I can somehow access 256K bytes using 128K of unique addresses.
I thought it might be in the half page access, but its not clear. Help me understand. Thanks!
I figured it out.
In HBUS mode the addressing accesses WORDS (2 Bytes)
In SPI mode the addressing accesses BYTES.
!DOH! Was pretty basic.