Renesas H8S Family, Hardware Manual

Page: 1050 / 1230

Section 25 Flash Memory
Rev. 1.00 Mar. 12, 2008 Page 1002 of 1178
REJ09B0403-0100
4. Bit rate
To facilitate error checking, the value (n) of clock select (CKS) in the serial mode register (SMR),
and the value (N) in the bit rate register (BRR), which are found from the peripheral operating
clock frequency (
φ
) and bit rate (B), are used to calculate the error rate to ensure that it is less than
4%. If the error is more than 4%, a bit rate error is generated. The error is calculated using the
following expression:
Error (%) = {[ ]
−
1}
×
100
(N + 1)
×
B
×
64
×
2
(2
×
n
−
1)
φ ×
10
6
When the new bit rate is selectable, the rate will be set in the register after sending ACK in
response. The host will send an ACK with the new bit rate for confirmation and the boot program
will response with that rate.
Confirmation H'06
•
Confirmation, H'06, (1 byte): Confirmation of a new bit rate
Response H'06
•
Response, H'06, (1 byte): Response to confirmation of a new bit rate
The sequence of new bit-rate selection is shown in figure 25.23.
Host
Boot program
Setting a new bit rate
H'06 (ACK)
Waiting for one-bit period
at the specified bit rate
H'06 (ACK) with the new bit rate
H'06 (ACK) with the new bit rate
Setting a new bit rate Setting a new bit rate
Figure 25.23 New Bit-Rate Selection Sequence