
Serial I/O Mode
199
Specifications in this manual are tentative and subject to change
Rev. E
MITSUBISHI MICROCOMPUTERS
M30245 Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
Standard Serial I/O Mode
The standard serial I/O mode serially inputs and outputs the software commands, addresses and data
needed to operate (read, program, erase, etc.) the internal flash memory. It uses a specific serial pro-
grammer to accomplish this. It is different from the parallel I/O mode because the CPU controls opera-
tions like rewriting the flash memory (using the CPU rewrite mode) and serially inputting data.
The standard serial I/O mode is entered by clearing the reset with the P50 (CE) pin set to a “H” level, the
P55 (EPM) pin set to a “L” level and the CNVss pin set to a “H” level. (For normal microprocessor mode,
set the CNVss pin to “L” level.)
A control program is written in the boot ROM area when the product is shipped from Mitsubishi. The standard
serial I/O mode cannot be used if the boot ROM area is rewritten in the parallel I/O mode. Figure 1.149 shows the
pin connections for the standard serial I/O mode. Table 1.69 lists the pin functions for standard serial IO mode.
There are two standard serial I/O modes that both require a purpose-specific serial programmer: clock synchro-
nous and clock asynchronous. Standard serial I/O switches between mode 1 (clock synchronous) and mode 2
(clock asynchronous) according to the level of the CLK1 pin when the reset is released. Serial data I/O uses
UART1 and transfers the data serially in 8-bit units.
To use standard serial I/O mode 1 (clock synchronous):
Set the CLK1 pin to “H” level and release the reset
This mode 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 asynchronous):
Set the CLK1 pin to “L” level and release the reset.
This mode uses the two UART1 pins RxD1 and TxD1.
In standard serial I/O mode, only the user ROM area indicated in Figure 1.140 can be rewritten. The boot ROM
cannot.
The standard serial I/O mode uses a 7-byte ID code. When there is data in the flash memory, commands sent
from the programmer are not accepted unless the ID codes are identical.
ID Code Check Function
The ID code check function can be used in serial I/O mode to protect the contents of the flash
memory from being read out or rewritten. If the contents of the flash memory are not blank, the
ID code sent from the serial programmer is compared with the ID code written in the flash. If the
ID codes are not identical, the commands sent from the serial programmer are not accepted.
Figure 1.150 shows the ID code store addresses. The ID code consists of 8-bit data: (beginning
with the first byte) 0FFFDF16, 0FFFE316, 0FFFEB16, 0FFFEF16, 0FFFF316, 0FFFF716, and
0FFFFB16. Write a program that has the ID code preset at these addresses.