Renesas H8S/2319 series Hardware Manual page 473

The BRR setting is found from the following formulas.
Asynchronous mode:
φ
N =
64 × 2
2n–1
Synchronous mode:
φ
N =
8 × 2
2n–1
Where B: Bit rate (bits/s)
N: BRR setting for baud rate generator (0 ≤ N ≤ 255)
φ: Operating frequency (MHz)
n: Baud rate generator input clock (n = 0 to 3)
(See the table below for the relation between n and the clock.)
n Clock
φ
0
φ/4
1
φ/16
2
φ/64
3
The bit rate error in asynchronous mode is found from the following formula:
Error (%) = {
× 10
6
– 1
× B
× 10
6
– 1
× B
SMR Setting
CKS1 CKS0
0 0
0 1
1 0
1 1
φ × 10
6
(N + 1) × B × 64 × 2
2n–1
– 1} × 100
Rev. 5.00, 12/03, page 443 of 1088