SH7052 datasheet(782/919 Pages) RENESAS

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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)

Figure 21.10 Automatic SCI Bit Rate Ajustment

When boot mode is initiated, the SH7054F 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 SH7054F 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 SH7054F. 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 SH7054F’s system clock

frequency, there will be a discrepancy between the bit rates of the host and the SH7054F. Set the

host transfer bit rate at 9,600 or 19,200 bps to operate the SCI properly.

Table 21.7 shows host transfer bit rates and system clock frequencies for which automatic

adjustment of the SH7054F bit rate is possible. The boot program should be executed within this

system clock range.

Table 21.7

System Clock Frequencies for which Automatic Adjustment of SH7054F Bit

Rate is Possible

Host Bit Rate

System Clock Frequency for Which Automatic Adjustment

of SH7054F Bit Rate is Possible

9,600 bps

20 to 40 MHz (input frequency: 5 to 10 MHz)

19,200 bps

20 to 40 MHz (input frequency: 5 to 10 MHz)

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