Renesas SH7641 - Manual (Page 757)

Section 19 Serial Communication Interface with FIFO (SCIF)
Rev. 4.00 Sep. 14, 2005 Page 707 of 982
REJ09B0023-0400
19.3.8 Bit Rate Register (SCBRR)
The bit rate register (SCBRR) is an 8-bit register that, together with the baud rate generator clock
source selected by the CKS1 and CKS0 bits in the serial mode register (SCSMR), determines the
serial transmit/receive bit rate.
The CPU can always read and write to SCBRR. SCBRR is initialized to H'FF by a power-on reset.
Each channel has independent baud rate generator control, so different values can be set in three
channels.
The SCBRR setting is calculated as follows:
• Asynchronous mode:
N = Ч 10 6 - 1
64 Ч 2 2n-1 × B
P φ
• Synchronous mode:
N = Ч 10 6 - 1
8 Ч 2 2n-1 × B
P
φ
B: Bit rate (bits/s)
N: SCBRR setting for baud rate generator (0
≤ N ≤ 255)
P
φ: Operating frequency for peripheral modules (MHz)
n: Baud rate generator clock source (n = 0, 1, 2, 3) (for the clock sources and values of
n, see table 19.2.)
Table 19.2 SCSMR Settings
SCSMR Settings
n Clock Source CKS1 CKS0
0 P φ 0 0
1 P φ/4 0 1
2 P
φ/16 1
0
3 P
φ/64 1
1
Note: The bit rate error in asynchronous is given by the following formula:
Error (%) = - 1
× 100
(N + 1) × B × 64 2n-1 × 2
P φ Ч 10 6