
1-225
Under
development
Specifications in this manual are tentative and subject to change
Rev. H
Serial I/O Mode 2 (Flash Memory Version)
MITSUBISHI MICROCOMPUTERS
M30222 Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
Standard Serial I/O mode 2 (clock asynchronous)
In standard serial I/O mode 2, software commands, addresses and data are input and output between the MCU
and peripheral units (serial programer, etc.) using 2-wire clock-asynchronized serial I/O (UART0). Standard serial
I/O mode 2 is engaged by releasing the reset with the P61 (CLK0) pin "L" level.
The TxD0 pin is for CMOS output. Data transfer is in 8-bit units with LSB first, 1 stop bit and parity OFF.
After the reset is released, connections can be established at 9,600 bps when initial communications (Figure
1.183) are made with a peripheral unit. However, this requires a main clock with a minimum 2 MHz input oscillation
frequency. Baud rate can also be changed from 9,600 bps to 19,200, 38,400 or 57,600 bps by executing software
commands. However, communication errors may occur because of the oscillation frequency of the main clock. If
errors occur, change the main clock's oscillation frequency and the baud rate.
After executing commands from a peripheral unit that requires time to erase and write data, as with erase and
program commands, allow a sufficient time interval or execute the read status command and check how process-
ing ended, before executing the next command.
Data and status registers in memory can be read after transmitting software commands. Status, such as the
operating state of the flash memory or whether a program or erase operation ended successfully or not, can be
checked by reading the status register. Here following are explained initial communications with peripheral units,
how frequency is identified and software commands.
Initial communications with peripheral units
After the reset is released, the bit rate generator is adjusted to 9,600 bps to match the oscillation frequency of
the main clock, by sending the code as prescribed by the protocol for initial communications with peripheral
units (Figure 1.83).
(1) Transmit "B016" from a peripheral unit. If the oscillation frequency input by the main clock is 10 MHz, the
MCU with internal flash memory outputs the "B016" check code. If the oscillation frequency is anything other
than 10 MHz, the MCU does not output anything.
(2) Transmit "0016" from a peripheral unit 16 times. (The MCU with internal flash memory sets the bit rate
generator so that "0016" can be successfully received.)
(3) The MCU with internal flash memory outputs the "B016" check code and initial communications end
successfully (see Note). Initial communications must be transmitted at a speed of 9,600 bps and a transfer
interval of a minimum 15 ms. Also, the baud rate at the end of initial communications is 9,600 bps.
Note: If the peripheral unit cannot receive "B016" successfully, change the oscillation frequency of the main
clock.