1.2.3 Memory Organization
Beyond the internal register space, memory on the MAXQ7665/MAXQ7666 microcontrollers is organized according to a Harvard archi-
tecture, with a separate address space and bus for program memory and data memory. Stack memory is also separate and is
accessed through a dedicated register set.
To provide additional memory map flexibility, an MMU allows data memory space to be mapped into a predefined program memory
segment, thus affording the possibility of code execution from data memory. Additionally, program memory space can be made acces-
sible as data space, allowing access to constant data stored in program memory. All memory is internal, and physical memory seg-
ments (other than the stack and register memories) can be accessed as either program memory or as data memory, but not both at
once.
1.2.3.1 Program Memory
The MAXQ7665/MAXQ7666 contain up to 64k x 16 (128kB) of flash memory, which normally serves as program memory. When exe-
cuting from the data SRAM or utility ROM, this memory is mapped to data space and can be used for lookup tables and similar func-
tions. Flash memory mapped into data space can be read from directly, like any other type of data memory. However, writing to flash
memory must be done by calling the in-application functions provided by the utility ROM. The utility ROM provides routines to carry
out the necessary operations (erase, write) on flash memory.
Table 1-3 summarizes the features of the flash memory supported in the MAXQ7665A–MAXQ7665D devices. The MAXQ7666 device
features a 256B data flash in addition to 16kB program flash. The MAXQ7666 flash is different from the MAXQ7665A–MAXQ7665D and
its features are summarized in Tables 1-4 and 1-5. Refer to the respective data sheets for additional information.
Program memory begins at address 0000h and is contiguous through the internal program memory. The actual size of the on-chip pro-
gram memory available for user application is product dependent. Given a 16-bit program address bus, the maximum program space
is 64kWords. Since the codewords are 16 bits, the program memory is, therefore, a 64k x 16 linear space.
MAXQ7665/MAXQ7666 User’s Guide
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