mc9s12xd256 Freescale Semiconductor, Inc, mc9s12xd256 Datasheet - Page 482

• Manufacturer Part Number: mc9s12xd256
• Description: Hcs12x Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Chapter 11 Serial Communication Interface (S12SCIV5)
11.3.2.1
Read: Anytime, if AMAP = 0. 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, if AMAP = 0.
The SCI baud rate register is used by to determine the baud rate of the SCI, and to control the infrared
modulation/demodulation submodule.
482
SBR[12:0]
TNP[1:0]
Reset
Reset
Field
IREN
6:5
4:0
7:0
7
W
W
R
R
SBR7
IREN
Infrared Enable Bit — This bit enables/disables the infrared modulation/demodulation submodule.
0 IR disabled
1 IR enabled
Transmitter Narrow Pulse Bits — These bits enable whether the SCI transmits a 1/16, 3/16, 1/32 or 1/4 narrow
pulse. See
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:
Note: The baud rate generator is disabled after reset and not started until the TE bit or the RE bit is set for the
Note: Writing to SCIBDH has no effect without writing to SCIBDL, because writing to SCIBDH puts the data in
SCI Baud Rate Registers (SCIBDH, SCIBDL)
0
0
7
7
When IREN = 0 then,
When IREN = 1 then,
Those two registers are only visible in the memory map if AMAP = 0 (reset
condition).
SCI baud rate = SCI bus clock / (16 x SBR[12:0])
SCI baud rate = SCI bus clock / (32 x SBR[12:1])
first time. The baud rate generator is disabled when (SBR[12:0] = 0 and IREN = 0) or (SBR[12:1] = 0 and
IREN = 1).
a temporary location until SCIBDL is written to.
Table
SBR6
TNP1
0
0
6
6
11-2.
Table 11-1. SCIBDH and SCIBDL Field Descriptions
Figure 11-3. SCI Baud Rate Register (SCIBDH)
Figure 11-4. SCI Baud Rate Register (SCIBDL)
MC9S12XDP512 Data Sheet, Rev. 2.17
TNP0
SBR5
0
0
5
5
SBR12
SBR4
NOTE
0
0
4
4
Description
SBR11
SBR3
0
0
3
3
SBR10
SBR2
0
0
2
2
Freescale Semiconductor
SBR9
SBR1
0
0
1
1
SBR8
SBR0
0
0
0
0