MC9S12P128 Datasheet, PDF (404/564 Pages) Freescale Semiconductor, Inc – S12 Microcontrollers

Serial Peripheral Interface (S12SPIV5)
12.3.2.3 SPI Baud Rate Register (SPIBR)
Module Base +0x0002
7
6
5
4
3
R
0
0
SPPR2
SPPR1
SPPR0
W
Reset
0
0
0
0
0
= Unimplemented or Reserved
2
SPR2
0
Figure 12-5. SPI Baud Rate Register (SPIBR)
Read: Anytime
Write: Anytime; writes to the reserved bits have no effect
1
SPR1
0
0
SPR0
0
Table 12-6. SPIBR Field Descriptions
Field
Description
6–4
SPI Baud Rate Preselection Bits — These bits specify the SPI baud rates as shown in Table 12-7. In master
SPPR[2:0] mode, a change of these bits will abort a transmission in progress and force the SPI system into idle state.
2–0
SPI Baud Rate Selection Bits — These bits specify the SPI baud rates as shown in Table 12-7. In master mode,
SPR[2:0] a change of these bits will abort a transmission in progress and force the SPI system into idle state.
The baud rate divisor equation is as follows:
BaudRateDivisor = (SPPR + 1) • 2^{(SPR + 1)}
Eqn. 12-1
The baud rate can be calculated with the following equation:
Baud Rate = BusClock / BaudRateDivisor
Eqn. 12-2
NOTE
For maximum allowed baud rates, please refer to the SPI Electrical
Specification in the Electricals chapter of this data sheet.
SPPR2
0
0
0
0
0
0
0
0
0
0
0
0
Table 12-7. Example SPI Baud Rate Selection (25 MHz Bus Clock) (Sheet 1 of 3)
SPPR1
0
0
0
0
0
0
0
0
0
0
0
0
SPPR0
0
0
0
0
0
0
0
0
1
1
1
1
SPR2
0
0
0
0
1
1
1
1
0
0
0
0
SPR1
0
0
1
1
0
0
1
1
0
0
1
1
SPR0
0
1
0
1
0
1
0
1
0
1
0
1
Baud Rate
Divisor
2
4
8
16
32
64
128
256
4
8
16
32
Baud Rate
12.5 Mbit/s
6.25 Mbit/s
3.125 Mbit/s
1.5625 Mbit/s
781.25 kbit/s
390.63 kbit/s
195.31 kbit/s
97.66 kbit/s
6.25 Mbit/s
3.125 Mbit/s
1.5625 Mbit/s
781.25 kbit/s
S12P-Family Reference Manual, Rev. 1.12
404
Freescale Semiconductor