Chapter 12 Serial Communication Interface (S12SCIV6)
S12ZVHY/S12ZVHL Family Reference Manual Rev. 1.05
480
Freescale Semiconductor
12.3.2.1
SCI Baud Rate Registers (SCIBDH, SCIBDL)
Read: Anytime, if AMAP = 0.
Write: Anytime, if AMAP = 0.
NOTE
Those two registers are only visible in the memory map if AMAP = 0 (reset
condition).
The SCI baud rate register is used by to determine the baud rate of the SCI, and to control the infrared
modulation/demodulation submodule.
Module Base + 0x0000
7
6
5
4
3
2
1
0
R
SBR15
SBR14
SBR13
SBR12
SBR11
SBR10
SBR9
SBR8
W
Reset
0
0
0
0
0
0
0
0
Figure 12-3. SCI Baud Rate Register (SCIBDH)
Module Base + 0x0001
7
6
5
4
3
2
1
0
R
SBR7
SBR6
SBR5
SBR4
SBR3
SBR2
SBR1
SBR0
W
Reset
0
1
0
0
0
0
0
0
Figure 12-4. SCI Baud Rate Register (SCIBDL)
Table 12-2. SCIBDH and SCIBDL Field Descriptions
Field
Description
SBR[15:0]
SCI Baud Rate Bits
— The baud rate for the SCI is determined by the bits in this register. The baud rate is
calculated two different ways depending on the state of the IREN bit.
The formulas for calculating the baud rate are:
When IREN = 0 then,
SCI baud rate = SCI bus clock / (SBR[15:0])
When IREN = 1 then,
SCI baud rate = SCI bus clock / (2 x SBR[15:1])
Note:
The baud rate generator is disabled after reset and not started until the TE bit or the RE bit is set for the
first time. The baud rate generator is disabled when (SBR[15:4] = 0 and IREN = 0) or (SBR[15:5] = 0 and
IREN = 1).
Note:
. User should write SCIBD by word access. The updated SCIBD may take effect until next RT clock start,
write SCIBDH or SCIBDL separately may cause baud generator load wrong data at that time,if second
write later then RT clock.
