SH7018 datasheet(349/431 Pages) RENESAS

349 / 431 page

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Automatic SCI Bit Rate Adjustment

Start

bit

Stop

bit

Low period (9 bits) measured (H'00 data)

High period

(1 or more bits)

When boot mode is initiated, the SH7018 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 SH7018 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 SH7018. If

reception cannot be performed normally, initiate boot mode again (power-on reset), and repeat the

above operations. Depending on the host’s transmission bit rate and the SH7018’s system clock

frequency, there will be a discrepancy between the bit rates of the host and the SH7018. To ensure

correct SCI operation, the host’s transfer bit rate should be set to 4800bps, 9600bps.

Table 16.6 shows host transfer bit rates and system clock frequencies for which automatic

adjustment of the SH7018 bit rate is possible. The boot program should be executed within this

system clock range.

Table 16.6

System Clock Frequencies for which Automatic Adjustment of SH7018 Bit Rate

is Possible

Host Bit Rate

System Clock Frequency for which Automatic Adjustment

of SH7018 Bit Rate is Possible

19200 bps

16 to 20 MHz

9600 bps

8 to 20 MHz

4800 bps

4 to 20 MHz

SH7018 Datasheet(PDF) 349 Page - Renesas Technology Corp