MC9S12KG128_10 Datasheet, PDF (334/606 Pages) Freescale Semiconductor, Inc – HCS12 Microcontrollers

Chapter 10 Serial Communications Interface (S12SCIV2) Block Description
10.3.2.1 SCI Baud Rate Registers (SCIBDH and SCHBDL)
Module Base + 0x_0000
7
6
R
0
0
W
Reset
0
0
5
4
3
2
1
0
0
SBR12
SBR11
SBR10
SBR9
SBR8
0
0
0
0
0
0
Module Base + 0x_0001
7
R
SBR7
W
6
SBR6
5
SBR5
4
SBR4
3
SBR3
2
SBR2
1
SBR1
0
SBR0
Reset
0
0
0
0
0
1
0
0
= Unimplemented or Reserved
Figure 10-3. SCI Baud Rate Registers (SCIBDH and SCIBDL)
The SCI Baud Rate Register is used by the counter to determine the baud rate of the SCI. The formula for
calculating the baud rate is:
SCI baud rate = SCI module clock / (16 x BR)
where:
BR is the content of the SCI baud rate registers, bits SBR12 through SBR0. The baud rate registers
can contain a value from 1 to 8191.
Read: Anytime. If only SCIBDH is written to, a read will not return the correct data until SCIBDL is
written to as well, following a write to SCIBDH.
Write: Anytime
Table 10-1. SCIBDH AND SCIBDL Field Descriptions
Field
Description
4–0
7–0
SBR[12:0]
SCI Baud Rate Bits — The baud rate for the SCI is determined by these 13 bits.
Note: The baud rate generator is disabled until the TE bit or the RE bit is set for the first time after reset. The
baud rate generator is disabled when BR = 0.
Writing to SCIBDH has no effect without writing to SCIBDL, since writing to SCIBDH puts the data in a
temporary location until SCIBDL is written to.
MC9S12KG128 Data Sheet, Rev. 1.16
334
Freescale Semiconductor