HD6432142 datasheet(748/1177 Pages) RENESAS

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Section 23 ROM (H8S/2148 F-ZTAT A-Mask Version, H8S/2147 F-ZTAT A-Mask Version, H8S/2144 F-ZTAT A-Mask Version)

Rev. 4.00 Sep 27, 2006 page 704 of 1130

REJ09B0327-0400

Automatic SCI Bit Rate Adjustment

Start

bit

Stop

bit

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

High period

(1 or more bits)

Figure 23.9 Automatic SCI Bit Rate Adjustment

When boot mode is initiated, the chip 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 chip 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 chip. 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 chips system clock frequency, there will be a

discrepancy between the bit rates of the host and the chip. To ensure correct SCI operation, the

host’s transfer bit rate should be set to (4800, 9600, or 19200) bps.

Table 23.7 shows typical host transfer bit rates and system clock frequencies for which automatic

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

system clock range.

Table 23.7

System Clock Frequencies for Which Automatic Adjustment of the Chips Bit

Rate Is Possible

Host Bit Rate

System Clock Frequency for Which Automatic Adjustment

of Bit Rate Is Possible

19200 bps

8 MHz to 20 MHz

9600 bps

4 MHz to 20 MHz

4800 bps

2 MHz to 18 MHz

On-Chip RAM Area Divisions in Boot Mode

In boot mode, the 1920-byte area from H'(FF)E880 to H'(FF) EFFF and the 128-byte area from

H'(FF)FF00 to H'(FF)FF7F is reserved for use by the boot program, as shown in figure 23.10. The

area to which the programming control program is transferred is H'(FF)E080 to H'(FF)E87F (2048

bytes). In the 64-kbyte version, this is a reserved area that is used only during the boot mode.

However, the 8-byte area from H'(FF)E080 to H'(FF)E087 is reserved for ID codes as shown in

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