SNIU028D February 2016 – September 2020 UCD3138 , UCD3138064 , UCD3138064A , UCD3138128 , UCD3138A , UCD3138A64
Two registers, the Memory Fine Base Address High Register, and the Memory Fine Base Address Low Register, combine to provide a start address for the memory block.
The Block Size field in the Memory Fine Base Address Register Low determines the size of the area for the memory block. The possible sizes range from 1KB, represented by a 1 in BLOCK_SIZE, to 16MB, represented by a 0xF. A zero in BLOCK_SIZE disables that memory from ever being selected.
To calculate the address provided by the MBBALRx, multiply it by 4 and include it in bits 8 to 15. For example, a 0x22 translates to 0x8800. A 0x24 translates to a 0x9000. There are other bits as well, for example an RONLY bit signifying that the memory is read only.
There is also a MS (for Memory Select) bit in only MFBALR0, which enables the entire DEC module. DEC stands for Memory Address DECode.