mc68hc908lj24 Freescale Semiconductor, Inc, mc68hc908lj24 Datasheet - Page 316

• Manufacturer Part Number: mc68hc908lj24
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Serial Peripheral Interface Module (SPI)
Data Sheet
316
MODFEN — Mode Fault Enable Bit
SPR1 and SPR0 — SPI Baud Rate Select Bits
Use this formula to calculate the SPI baud rate:
where:
This read/write bit, when set to 1, allows the MODF flag to be set. If
the MODF flag is set, clearing the MODFEN does not clear the MODF
flag. If the SPI is enabled as a master and the MODFEN bit is low,
then the SS pin is available as a general-purpose I/O.
If the MODFEN bit is set, then this pin is not available as a general-
purpose I/O. When the SPI is enabled as a slave, the SS pin is not
available as a general-purpose I/O regardless of the value of
MODFEN. (See
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
In master mode, these read/write bits select one of four baud rates as
shown in
Reset clears SPR1 and SPR0.
CGMOUT = base clock output of the clock generator module (CGM)
BD = baud rate divisor
Serial Peripheral Interface Module (SPI)
SPR1 and SPR0
Baud rate
Table
Table 14-4. SPI Master Baud Rate Selection
00
01
10
11
14-4. SPR1 and SPR0 have no effect in slave mode.
14.8.2 Mode Fault
14.13.4 SS (Slave
=
CGMOUT
------------------------- -
2 BD
×
Select).)
Error.)
Baud Rate Divisor (BD)
MC68HC908LJ24/LK24 — Rev. 2.1
128
32
2
8
Freescale Semiconductor