Write/Erase Modes - Fujitsu MB90390 Series Hardware Manual

28.3

Write/Erase Modes

The flash memory can be accessed in two different ways: Flash memory mode and
alternative mode. Flash memory mode enables data to be directly written to or erased
from the external pins. Alternative mode enables data to be written to or erased from
the CPU via the internal bus. Use the mode external pins to select the mode.
■ Flash Memory Mode
The CPU stops when the mode pins are set to "111
interface circuit is connected directly to ports 0, 1, 2, 3, 4 and 5, enabling direct control from the external
pins. This mode makes the MCU seem like a standard flash memory to the external pins, and write/erase
can be performed using a flash memory programmer.
In flash memory mode, all operations supported by the flash memory automatic algorithm can be used.
■ Alternative Mode
The flash memory is located in the F8/F9 to FF banks in the CPU memory space, and like ordinary mask
ROM, can be read-accessed and program-accessed from the CPU via the flash memory interface circuit.
Since writing/erasing the flash memory is performed by instructions from the CPU via the flash memory
interface circuit, this mode allows rewriting even when the MCU is soldered on the target board.
Sector protect operations cannot be performed in these modes.
Note:
Writing/erasing the flash memory is not specified at all machine clock frequencies. Refer to the AC
Characteristics section of the data sheet.
■ Flash Memory Control Signals
Table 28.3-1 lists the flash memory control signals.
There is almost a one-to-one correspondence between the flash memory control signals and the external
pins of the MBM29LV200. The V
and MD2 instead of A9, RESET, and OE for the MBM29LV200.
In flash memory mode, the external data bus signal width is limited to 8 bits, enabling only one-byte
access. The DQ15 to DQ8 pins are not supported. The BYTE pin should always be set to "0".
" while the reset signal is asserted. The flash memory
B
(12 V) pins required by the sector protect operations are MD0, MD1,
ID
CHAPTER 28 3M-BIT FLASH MEMORY
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