M37905F8CFP Datasheet, PDF (15/35 Pages) Mitsubishi Electric Semiconductor – 16-BIT CMOS MICROCOMPUTER

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Flash Memory Serial I/O Mode
In the flash memory serial I/O mode, addresses, data, and software
commands, which are required to read/program/erase the internal
flash memory, are serially input and output with a fewer pins and the
dedicated serial programmer.
In this mode, being different from the flash memory parallel I/O
mode, the CPU controls reprogramming of the flash memory (using
the CPU reprogramming mode), serial input of the reprogramming
data, etc.
The reprogramming control firmware for the flash memory serial I/O
mode has been stored in the boot ROM area on shipment of the
product from us. Note that, then, the flash memory serial I/O mode
will become unavailable if the boot ROM area has been repro-
grammed in the flash memory parallel I/O mode.
Note that, also, this reprogramming control firmware for the flash
memory serial I/O mode is subject to change.
Figures 5 and 6 show the pin connections in the flash memory serial
I/O mode.
The three pins, SCLK, SDA, and BUSY, are used to input and output
serial data.
The SCLK pin is the input pin of external transfer clocks. The SDA
pin is the I/O pin of transmit and receive data, and its output acts as
the N-channel open-drain output. To the SDA pin, connect an exter-
nal pullup resistor (about 1 kΩ). The BUSY pin is the output pin of the
BUSY flag (CMOS output) and goes “H” during BUSY periods owing
to a certain operation, such as transmit, receive, erase, program-
ming, etc.
Transmit and receive data are serially transferred 8 bits at a time.
In the flash memory serial I/O mode, only the user ROM area can be
reprogrammed; the boot ROM area is not accessible.
Addresses FF9016 to FF9F16 are the reserved area for the serial
programmer. Therefore, when the user uses the flash memory serial
I/O mode, do not program to this area.
MITSUBISHI MICROCOMPUTERS
M37905F8CFP, M37905F8CSP
16-BIT CMOS MICROCOMPUTER
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