Serial Peripheral Interface (S12SPIV5)
S12XS Family Reference Manual, Rev. 1.13
442
Freescale Semiconductor
15.3.2.3
SPI Baud Rate Register (SPIBR)
Read: Anytime
Write: Anytime; writes to the reserved bits have no effect
The baud rate divisor equation is as follows:
BaudRateDivisor = (SPPR + 1)
•
2
(SPR + 1)
Eqn. 15-1
The baud rate can be calculated with the following equation:
Baud Rate = BusClock / BaudRateDivisor
Eqn. 15-2
NOTE
For maximum allowed baud rates, please refer to the SPI Electrical
Specification in the Electricals chapter of this data sheet.
Module Base +0x0002
7
6
5
4
3
2
1
0
R
0
SPPR2
SPPR1
SPPR0
0
SPR2
SPR1
SPR0
W
Reset
0
0
0
0
0
0
0
0
= Unimplemented or Reserved
Figure 15-5. SPI Baud Rate Register (SPIBR)
Table 15-6. SPIBR Field Descriptions
Field
Description
6–4
SPPR[2:0]
SPI Baud Rate Preselection Bits
—
These bits specify the SPI baud rates as shown in
. In master
mode, a change of these bits will abort a transmission in progress and force the SPI system into idle state.
2–0
SPR[2:0]
SPI Baud Rate Selection Bits
—
These bits specify the SPI baud rates as shown in
. In master mode,
a change of these bits will abort a transmission in progress and force the SPI system into idle state.
Table 15-7. Example SPI Baud Rate Selection (25 MHz Bus Clock) (Sheet 1 of 3)
SPPR2
SPPR1
SPPR0
SPR2
SPR1
SPR0
Baud Rate
Divisor
Baud Rate
0
0
0
0
0
0
2
12.5 Mbit/s
0
0
0
0
0
1
4
6.25 Mbit/s
0
0
0
0
1
0
8
3.125 Mbit/s
0
0
0
0
1
1
16
1.5625 Mbit/s
0
0
0
1
0
0
32
781.25 kbit/s
0
0
0
1
0
1
64
390.63 kbit/s
0
0
0
1
1
0
128
195.31 kbit/s
0
0
0
1
1
1
256
97.66 kbit/s
0
0
1
0
0
0
4
6.25 Mbit/s
0
0
1
0
0
1
8
3.125 Mbit/s
0
0
1
0
1
0
16
1.5625 Mbit/s
0
0
1
0
1
1
32
781.25 kbit/s
Summary of Contents for MC9S12XS128
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