Renesas SH7041 Series, Hardware Manual, Page: 739 / 923

701
Automatic SCI Bit Rate Adjustment
Start
Bit
Stop
Bit
D0 D1 D2 D3 D4 D5 D6 D7
High period of
more than 1 bit
Low period (9 bits) measured (H'00 data)
Figure 22.10 Automatic SCI Bit Rate Adjustment
When boot mode is initiated, the LSI measures the low period of the asynchronous SCI
communication data (H'00) transmitted continuously from the host. The SCI transmit/receive
format should be set as follows: 8-bit data, 1 stop bit, no parity. The LSI calculates the bit rate of
the transmission from the host from the measured low period, and transmits one H'00 byte to the
host to indicate the end of bit rate adjustment. The host should confirm that this adjustment end
indication (H'00) has been received normally, and transmit one H'55 byte to the LSI. If reception
cannot be performed normally, initiate boot mode again (reset), and repeat the above operations.
Depending on the host’s transmission bit rate and the LSI’s system clock frequency, there will be
a discrepancy between the bit rates of the host and the LSI. To ensure correct SCI operation, the
host's transfer bit rate should be set to 9,600 or 4,800 bps.
Table 22.7 shows host transfer bit rates and system clock frequencies for which automatic
adjustment of the LSI bit rate is possible. The boot program should be executed within this system
clock range.
Table 22.7 System Clock Frequencies for which Automatic Adjustment of LSI Bit Rate is
Possible
Host Bit Rate
System Clock Frequency for which Automatic Adjustment
of LSI Bit Rate is Possible
9,600 bps 8 to 28.7 MHz
4,800 bps 4 to 20 MHz