Datasheet

Section 19 ROM
Rev.6.00 Sep. 27, 2007 Page 761 of 1268
REJ09B0220-0600
Automatic SCI Bit Rate Adjustment: When boot mode is initiated, the H8S/2329B F-ZTAT
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 chip’s 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 9,600 or 19,200 bps.
Table 19.10 shows typical host transfer bit rates and system clock frequencies for which automatic
adjustment of the MCU’s bit rate is possible. The boot program should be executed within this
system clock range.
Start
bit
Stop
bit
D0 D1 D2 D3 D4 D5 D6 D7
Low period (9 bits) measured (H'00 data)
High period
(1 or more bits)
Figure 19.11 Automatic SCI Bit Rate Adjustment
Table 19.10 System Clock Frequencies for which Automatic Adjustment of H8S/2329B
F-ZTAT Bit Rate is Possible
Host Bit Rate
System Clock Frequency for which Automatic Adjustment
of H8S/2329B F-ZTAT Bit Rate is Possible
19,200 bps 16 MHz to 25 MHz
9,600 bps 8 MHz to 25 MHz
On-Chip RAM Area Divisions in Boot Mode: In boot mode, the 2-kbyte area from H'FF7C00 to
H'FF83FF is reserved for use by the boot program, as shown in figure 19.12. The area to which the
programming control program is transferred is H'FF8400 to H'FFFBFF. The boot program area
can be used when the programming control program transferred into RAM enters the execution
state. A stack area should be set up as required.