M16C80 Datasheet, PDF (306/358 Pages) Renesas Technology Corp – RENESAS 16-BIT SINGLE-CHIP MICROCOMPUTER M16C FAMILY / M16C/80 SERIES

M16C/80 Group
32. Standard serial I/O mode
32. 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 the factory. 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 31.1 and 31.3 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
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 32.17can 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.
Rev.1.00 Aug. 02, 2005 ^{Page 295} of 329
REJ09B0187-0100