Fujitsu F2MC-16L Series User Manual page 10

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The board has various modes to use the on-board RAM in different configurations. On User

Reset the memory mapping is changed to User Mode. So, the user RAM that holds the

application program can be executed in that case. On Monitor Reset the board is initialised to

its defaults, after that it switched to User Mode mapping.

Only a small RAM area (90000h..927FFh) is reserved for monitor variables and data. A few

memory mapped control registers (see memory map) are located in a so-called control bank

(bank 7). Three of the four control registers linked to LEDs can be used for simple user

program indicators.

The lower memory area allows access to the controller built-in RAM, general register banks,

EI²OS descriptors (Extended Intelligent I/O Service) and the controller peripherals. Within the

I/O area 64 Bytes of external memory are accessible via special I/O instructions.

The board provides also control signals for memory areas not taken by any device of the board.

NOTE: Although the MB90670/675 controllers have a 24 bit address size only 20 bits are

used for accessing external memory. Therefore, only 16 physical pages, each 64 KB

of size, are available. Address bits 16 ...19 select one of these pages. Hence, it follows

that address FF1234h and address 0F1234h accesses the same cell in page F.

Only page 0 is exceptional. If the upper four address bits (20 ... 23) are all zero the

absolute page 0' is selected. This page contains the controller peripherals, internal

RAM and parts of external RAM of external page 0. Any other value than zero of the

highest four address bits selects the external page 0. The upper bits (20...23) have no

function referring to the mapping if any other page than page 0 is addressed.

However, the controller provides an "Auto-Cycle" function to prolong external access

time (see MB90675 User Manual). Referring to this function the upper address bits

(20...23) select three areas (0...7, 8...F and absolute page 0') with separate

programmable "Auto-Cycle" number.

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FUJITSU MB90675-Evaluation Board - User Manual

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Mb90675 series