MC68HC05C8A Datasheet, PDF (57/116 Pages) Motorola, Inc – Microcontrollers

SCI Input/Output (I/O) Registers
9.5.5 Baud Rate Register
The baud rate register (BAUD) selects the baud rate for both the receiver and the transmitter.
Address: $000D
Bit 7
6
5
4
3
2
Read:
0
Write:
0
SCP1
SCP0
0
SCR2
Reset: 0
0
0
0
0
U
U = Unaffected
Figure 9-8. Baud Rate Register (BAUD)
1
SCR2
U
Bit 0
SCR0
U
SCP1 and SCP0 — SCI Prescaler Select Bits
These read/write bits control prescaling of the baud rate generator clock, as shown in Table 9-1.
Resets clear both SCP1 and SCP0.
Table 9-1. Baud Rate Generator Clock Prescaling
SCP0–SCP1
00
01
10
11
Baud Rate Generator Clock
Internal clock divided by 1
Internal clock divided by 3
Internal clock divided by 4
Internal clock divided by 13
SCR2–SCR0 — SCI Baud Rate Select Bits
These read/write bits select the SCI baud rate, as shown in Table 9-2. Reset has no effect on the
SCR2–SCR0 bits.
Table 9-2. Baud Rate Selection
SCR2–SCR0
000
001
010
011
100
101
110
111
SCI Baud Rate (Baud)
Prescaled clock divided by 1
Prescaled clock divided by 2
Prescaled clock divided by 4
Prescaled clock divided by 8
Prescaled clock divided by 16
Prescaled clock divided by 32
Prescaled clock divided by 64
Prescaled clock divided by 128
Table 9-3 shows all possible SCI baud rates derived from crystal frequencies of 2 MHz, 4 MHz, and
4.194304 MHz.
MC68HC05C8A • MC68HCL05C8A • MC68HSC05C8A Data Sheet, Rev. 5.1
Freescale Semiconductor
57