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HARDWARE
3850 Group (Spec. H) User’s Manual
FUNCTIONAL DESCRIPTION
1-56
Standard serial I/O mode
The standard serial I/O mode inputs and outputs the software com-
mands, addresses and data needed to operate (read, program,
erase, etc.) the internal flash memory. This I/O is clock synchronized
serial. This 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 re-
write mode), rewrite data input and so forth. The standard serial I/O
mode is started by connecting “H” to the P26 (SCLK1) pin and the
P41(INT0) pin and “H” to the CNVSS pin (when VCC = 4.5 V to 5.5 V,
connect to VCC; when VCC = 2.7 V to 4.5 V, supply 4.5 V to 5.5 V to
Vpp from an external source), and releasing the reset operation. (In
the ordinary command mode, set CNVss pin to “L” level.)
This control program is written in the boot ROM area when the prod-
uct is shipped from Renesas Technology Corp. Accordingly, 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. Figure 56
shows the pin connections for the standard serial I/O mode. Serial
data I/O uses SI/O1 data serially in 8-bit units.
To use standard serial I/O mode. The operation uses the four SI/O1
pins SCLK1, RxD, TxD and SRDY1 (BUSY). The SCLK1 pin is the
transfer clock input pin through which an external transfer clock is
input. The TxD pin is for CMOS output. The SRDY1 (BUSY) pin out-
puts an “L” level when ready for reception and an “H” level when
reception starts.
In the standard serial I/O mode, only the user ROM area indicated in
Figure 44 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, commands sent from the periph-
eral unit (programmer) are not accepted unless the ID code
matches.
Overview of standard serial I/O mode
In standard serial I/O mode, software commands, addresses and
data are input and output between the MCU and peripheral units
(serial programer, etc.) using 4-wire clock-synchronized serial I/O
(SI/O1).
In reception, software commands, addresses and program data are
synchronized with the rise of the transfer clock that is input to the
SCLK1 pin, and are then input to the MCU via the RxD pin. In trans-
mission, the read data and status are synchronized with the fall of
the transfer clock, and output from the TxD pin.
The TxD pin is for CMOS output. Transfer is in 8-bit units with LSB
first.
When busy, such as during transmission, reception, erasing or pro-
gram execution, the SRDY1 (BUSY) pin is “H” level. Accordingly, al-
ways start the next transfer after the SRDY1 (BUSY) pin is “L” level.
Also, data and status registers in memory can be read after inputting
software commands. Status, such as the operating state of the flash
memory or whether a program or erase operation ended success-
fully or not, can be checked by reading the status register. Here fol-
lowing are explained software commands, status registers, etc.