Datasheet

Chapter 8 Serial Communication Interface (SCIV4) Block Description
MC9S12E256 Data Sheet, Rev. 1.10
Freescale Semiconductor 255
8.4.2.1 SCI Baud Rate Registers (SCIBDH and SCIBDL)
Read: anytime
Module Base + 0x0000
76543210
R
IREN TNP1 TNP0 SBR12 SBR11 SBR10 SBR9 SBR8
W
Reset 0 0 0 00000
Figure 8-3. SCI Baud Rate Register High (SCIBDH)
Table 8-2. SCIBDH Field Descriptions
Field Description
7
IREN
Infrared Enable Bit — This bit enables/disables the infrared modulation/demodulation submodule.
0 IR disabled
1 IR enabled
6:5
TNP[1:0]
Transmitter Narrow Pulse Bits — These bits determine if the SCI will transmit a 1/16, 3/16, 1/32, or 1/4 narrow
pulse. Refer to Table 8-4.
4:0
SBR[11:8]
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 module clock / (16 x SBR[12:0])
When IREN = 1 then,
SCI baud rate = SCI module clock / (32 x SBR[12:1])
Module Base + 0x0001
76543210
R
SBR7 SBR6 SBR5 SBR4 SBR3 SBR2 SBR1 SBR0
W
Reset 0 0 0 00100
Figure 8-4. SCI Baud Rate Register Low (SCIBDL)
Table 8-3. SCIBDL Field Descriptions
Field Description
7:0
SBR[7:0]
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 module clock / (16 x SBR[12:0])
When IREN = 1 then,
SCI baud rate = SCI module clock / (32 x SBR[12:1])