MC68HC908MR8 Datasheet, PDF (277/372 Pages) Motorola, Inc – Microcontrollers

Serial Communications Interface (SCI)
I/O Registers
SCP1 and SCP0 — SCI Baud Rate Prescaler Bits
These read/write bits select the baud rate prescaler divisor as shown
in Table 13-5. Reset clears SCP1 and SCP0.
Table 13-5. SCI Baud Rate Prescaling
SCP1:SCP0
00
01
10
11
Prescaler Divisor (PD)
1
3
4
13
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
000
001
010
011
100
101
110
111
Baud Rate Divisor (BD)
1
2
4
8
16
32
64
128
Use this formula to calculate the SCI baud rate:
Baud rate = f_OP / 64 x PD x BD
where:
f_OP = clock source (f_Bus)
PD = prescaler divisor
BD = baud rate divisor
Table 13-7 shows the SCI baud rates that can be generated with a
4.00-MHz crystal and the CGM set for an f_OP of 8.00 MHz and with a
4.9152-MHz crystal with the CGM set for an an f_OP of 7.3728 MHz.
MC68HC908MR8 — Rev 4.1
Technical Data
Freescale Semiconductor
Serial Communications Interface (SCI)
277