MC9S08AW16CFUE Datasheet, PDF (186/324 Pages) Freescale Semiconductor, Inc – MC9S08AW60 Features

Chapter 11 Serial Communications Interface (S08SCIV2)
Refer to the direct-page register summary in the Memory chapter of this data sheet for the absolute address
assignments for all SCI registers. This section refers to registers and control bits only by their names. A
Freescale-provided equate or header file is used to translate these names into the appropriate absolute
addresses.
11.2.1 SCI Baud Rate Registers (SCIxBDH, SCIxBHL)
This pair of registers controls the prescale divisor for SCI baud rate generation. To update the 13-bit baud
rate setting [SBR12:SBR0], first write to SCIxBDH to buffer the high half of the new value and then write
to SCIxBDL. The working value in SCIxBDH does not change until SCIxBDL is written.
SCIxBDL is reset to a non-zero value, so after reset the baud rate generator remains disabled until the first
time the receiver or transmitter is enabled (RE or TE bits in SCIxC2 are written to 1).
7
6
5
4
3
2
R
0
0
0
SBR12
SBR11
SBR10
W
Reset
0
0
0
0
0
0
= Unimplemented or Reserved
Figure 11-4. SCI Baud Rate Register (SCIxBDH)
1
SBR9
0
0
SBR8
0
Table 11-1. SCIxBDH Register Field Descriptions
Field
Description
4:0
Baud Rate Modulo Divisor — These 13 bits are referred to collectively as BR, and they set the modulo divide
SBR[12:8] rate for the SCI baud rate generator. When BR = 0, the SCI baud rate generator is disabled to reduce supply
current. When BR = 1 to 8191, the SCI baud rate = BUSCLK/(16×BR). See also BR bits in Table 11-2.
R
W
Reset
7
SBR7
0
6
SBR6
5
SBR5
4
SBR4
3
SBR3
2
SBR2
0
0
0
0
1
Figure 11-5. SCI Baud Rate Register (SCIxBDL)
1
SBR1
0
0
SBR0
0
Table 11-2. SCIxBDL Register Field Descriptions
Field
Description
4:0
Baud Rate Modulo Divisor — These 13 bits are referred to collectively as BR, and they set the modulo divide
SBR[12:8] rate for the SCI baud rate generator. When BR = 0, the SCI baud rate generator is disabled to reduce supply
current. When BR = 1 to 8191, the SCI baud rate = BUSCLK/(16×BR). See also BR bits in Table 11-1.
MC9S08AW60 Data Sheet, Rev 2
186
Freescale Semiconductor