Flash Access Mode Switching - Fujitsu MB91460 SERIES FR60 User Manual

4. Flash Access Mode Switching

On MB91460 series flash devices it is possible to switch between different flash access modes. These modes are
depending on device type.
Device
MB91F467DA
MB91F469GA
MB91F464AA
MB91F465KA
The 16bit mode is intended basically for flash programming, so program execution from flash is prohibited anyway.
The 32bit and 64bit modes, however, are intended for program execution from flash. Since switching between
these modes directly from an application located in the flash is prohibited it is necessary to locate the switching
routine either in RAM or use the available routine in the Boot ROM:
This routine is located at address 0xBF60 for all MB91F46x devices. To call this function two parameters are
expected in CPU registers R4 and R5:
R4: 2bits (LSB of register) for setting the flash access mode
b'00:
b'01:
b'1x:
R5: 16bits for setting wait time
The wait time should be in the range of some 100ns after switching the flash access mode for stabilization of the
Flash-ROM. The wait function is a simple delay loop that needs about 3 CPU cycles for one run. The value in R5
represents the number of runs through this delay loop.
Example (time for 1 run through delay loop):
30 ns @ 100MHz CPU clock
47 ns @ 64MHz CPU clock
94 ns @ 32MHz CPU clock
500 ns @ 2MHz CPU clock
After leaving this delay loop, the switching function will return to the application.
16bit access
read/write
read/write
read/write
read/write
32bit read/write mode
16bit read/write mode
64bit read only mode
Chapter 53 Fixed Mode-Reset Vector / BOOT-ROM
32bit access
read/write
read/write
read
read
min. 4-5 runs
min. 3 runs
min. 2 runs
min. 1 runs
4.Flash Access Mode Switching
64bit access
read
read
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