Serial flash boot (boot modes 1 and 3) is described in the application note "High-speed Read/Write Serial Flash Memory Using
the Renesas Serial Peripheral lnterface" (Document number: REJ06B0889-0100).
Serial flash boot reads the program data from the serial flash memory which is connected to the MCU.
Note that the serial flash memory must satisfy the timing described in Tables 4 and 5 on application note page 10.
Internal ROM program to boot which is included in the CPU sets RSPI channel 0 as follows:
(1) Bit rate register (SPBR)
Boot mode 1 (BΦ/2): 0x00 (division ratio: 2)
Boot mode 3 (BΦ/4): 0x01 (division ratio: 4)
(2) Command register (SPCMD)
SCKDEN bit = b'0 (RSPCK delay is 1 RSPCK)
SLNDEN bit = b'0 (SSL negation delay is 1 RSPCK)
SPNDEN bit = b'0 (0: Next access delay is 1 RSPCK + 2 BΦ)
BRDV [1:0] bits = b'00 (specify the base bit rate)