Freescale Semiconductor MC68HC908MR32 manual SCI Baud Rate Selection, Baud Rate Divisor BD

Serial Communications Interface Module (SCI)

SCR2–SCR0 — SCI Baud Rate Select Bits

These read/write bits select the SCI baud rate divisor as shown in Table 13-6. Reset clears SCR2–SCR0.

Table 13-6. SCI Baud Rate Selection

SCR2:SCR1:SCR0	Baud Rate Divisor (BD)
000	1
001	2
010	4
011	8
100	16
101	32
110	64
111	128

Use this formula to calculate the SCI baud rate:

fOP

Baud rate = ------------------------------------

64 ⋅ PD ⋅ BD

where:

fOP = internal operating frequency PD = prescaler divisor

BD = baud rate divisor

Table 13-7shows the SCI baud rates that can be generated with a 4.9152-MHz crystal with the CGM set for an fOP of 7.3728 MHz and the CGM set for an fOP of 4.9152 MHz.

MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1

178 Freescale Semiconductor