Datasheet

Section 7 ROM
Page 190 of 982 REJ09B0465-0300 Rev. 3.00
Sep 17, 2010
H8S/20103, H8S/20203, H8S/20223, H8S/20115, H8S/20215, H8S/20235 Group
(m) New Bit-Rate Selection
In response to a new bit-rate selection command, the boot program changes the bit rate settings to
those of the specified one, and responds to the acknowledgement from the host at the new bit rate.
The new bit-rate selection command should be transmitted after the clock-mode selection
command.
Command H'3F Size Bit rate Input frequency
Number of
frequency
division
ratio types
Frequency
division
ratio 1
Frequency
division
ratio 2
SUM
Command H'3F (1 byte): New bit-rate selection
Size (1 byte): The total size of the bit-rate, input-frequency, number-of-frequency-division-
ratio-types, and frequency-division-ratio fields.
Bit rate (2 bytes): New bit rate
The value to be set here is obtained by dividing the desired bit rate by 100. (For example, to
select the bit rate of 19200 bps, 19200 is divided by 100 to be 192, and so H'00C0 should be
set.)
Input frequency (2 bytes): The frequency of the clock input to the boot program.
Bit 15: Clock source (0: external clock, 1: on-chip oscillator)
Bits 14 to 0: A frequency of the clock to be input to the device
The value to be set here is obtained by multiplying the input frequency (MHz; to the second
decimal place) by 100. (For example, to select the input frequency of 20.00 MHz, 20.00 is
multiplied by 100 to be 2000, and so H'07D0 should be set.)
Number of frequency division ratio types (1 byte): The number of selectable frequency
division ratios for the device.
(The value is usually H'02 because the main and peripheral module operating frequencies can
be usually selected.)
Frequency division ratio 1 (1 byte): Frequency division ratio for the main operating frequency.
The negative numerical value by which the frequency is divided. (Example: H'FE (-2) when
the frequency is divided by two.)