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Appendix Standard Serial I/O Mode (Flash Memory Version)

Mitsubishi microcomputers

M16C / 62A Group

SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

1-239

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-

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leased, which is done when the P50 (CE) pin is "H" level, the P55 (EPM) pin "L" level and the CNVss pin "H"

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 1.29.1 and 1.29.2 show the pin connections for the standard

serial I/O mode. Serial data I/O uses UART1 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 CLK1 pin when the reset is released.

To use standard serial I/O mode 1 (clock synchronized), set the CLK1 pin to "H" level and release the reset.

The operation uses the four UART1 pins CLK1, RxD1, TxD1 and RTS1 (BUSY). The CLK1 pin is the transfer

clock input pin through which an external transfer clock is input. The TxD1 pin is for CMOS output. The

RTS1 (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 CLK1 pin to "L" level and release the

reset. The operation uses the two UART1 pins RxD1 and TxD1.

In the standard serial I/O mode, only the user ROM area indicated in Figure 1.29.19 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.

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