MC68HC08AS20 Datasheet, PDF (303/386 Pages) Freescale Semiconductor, Inc – M68HC08 Microcontrollers

If the MODFEN bit is low, the level of the SS pin does not affect the
operation of an enabled SPI configured as a master. For an enabled
SPI configured as a slave, having MODFEN low only prevents the
MODF flag from being set. It does not affect any other part of SPI
operation. (See 18.7.2 Mode Fault Error.)
SPR1 and SPR0 — SPI Baud Rate Select Bits
In master mode, these read/write bits select one of four baud rates as
shown in Table 18-6. SPR1 and SPR0 have no effect in slave mode.
Reset clears SPR1 and SPR0.
Table 18-6. SPI Master Baud Rate Selection
SPR1:SPR0
00
01
10
11
Baud Rate Divisor (BD)
2
8
32
128
Use the following formula to calculate the SPI baud rate:
where:
Baud rate
=
C-----2G-----M_{×----BO-----DU----T---}
=
B-----u---s-----c---l-o---c---k--
BD
CGMOUT = base clock output of the clock generator module (CGM),
see Section 8. Clock Generator Module (CGM).
BD = baud rate divisor
MC68HC08AS20 — Rev. 4.1
Freescale Semiconductor
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