Appendix Standard Serial I/O Mode (Flash Memory Version)
Mitsubishi microcomputers
M30201 Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
146
Standard serial I/O mode
The standard serial I/O mode inputs and outputs the software commands, addresses and data needed to
operate (read, program, erase, etc.) the internal flash memory. This I/O is serial. There are actually two
standard serial I/O modes: mode 1, which is clock synchronized, and mode 2, which is asynchronized. Both
modes require a purpose-specific peripheral unit.
The standard serial I/O mode is different from the parallel I/O mode in that the CPU controls flash memory
rewrite (uses the CPU's rewrite mode), rewrite data input and so forth. It is started when the reset is re-
leased, which is done when the P52 (SCLK) pin is "H" level, the CNVss pin "VppH" level. (In the ordinary
command mode, set CNVss pin to "L" level.)
This control program is written in the boot ROM area when the product is shipped from Mitsubishi. Accord-
ingly, make note of the fact that the standard serial I/O mode cannot be used if the boot ROM area is
rewritten in the parallel I/O mode. Figures 1.105 and 1.106 show the pin connections for the standard serial
I/O mode. Serial data I/O uses UART0 and transfers the data serially in 8-bit units. Standard serial I/O
switches between mode 1 (clock synchronized) and mode 2 (clock asynchronized) according to the level of
P53 (BUSY) pin when the reset is released.
To use standard serial I/O mode 1 (clock synchronized), set the P53 (BUSY) pin to "H" level and release the
reset. The operation uses the four UART0 pins CLK0, RxD0, TxD0 and P53 (BUSY). The CLK0 pin is the
transfer clock input pin through which an external transfer clock is input. The TxD0 pin is for CMOS output.
The P53 (BUSY) pin outputs an "L" level when ready for reception and an "H" level when reception starts.
To use standard serial I/O mode 2 (clock asynchronized), set the P53 (BUSY) pin to "L" level and release
the reset. The operation uses the two UART0 pins RxD0 and TxD0.
In the standard serial I/O mode, only the user ROM area indicated in Figure 1.96 can be rewritten. The boot
ROM cannot.
In the standard serial I/O mode, a 7-byte ID code is used. When there is data in the flash memory, com-
mands sent from the peripheral unit are not accepted unless the ID code matches.