deveopmen
Appendix Standard Serial I/O Mode (Flash Memory Version)
Rev.B2 for proof reading
Mitsubishi Microcomputers
M32C/83 group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
400
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 P5
0
(CE) pin is "H" level, the P5
5
(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 1.35.1 to 1.35.3 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
CLK
1
pin when the reset is released.
To use standard serial I/O mode 1 (clock synchronized), set the CLK
1
pin to "H" level and the TxD
1
pin to "L"
level, and release the reset. The CLK
1
pin is connected to Vcc via pull-up resistance and the TxD
1
is
connected to Vss via pull-down resistance. The operation uses the four UART1 pins CLK
1
, RxD
1
, TxD
1
and
RTS
1
(BUSY). The CLK
1
pin is the transfer clock input pin through which an external transfer clock is input.
The TxD
1
pin is for CMOS output. The RTS
1
(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 CLK
1
pin to "L" level and release the reset.
The operation uses the two UART1 pins RxD
1
and TxD
1
.
In the standard serial I/O mode, only the user ROM area indicated in Figure 1.35.20 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 (programmer) are not accepted unless the ID code matches.