MC68HC908QC16_07 Datasheet, PDF (187/274 Pages) Freescale Semiconductor, Inc – Microcontrollers

Registers
SPTE — SPI Transmitter Empty Bit
This clearable, read-only flag is set each time the transmit data register transfers a byte into the shift
register. SPTE generates an SPTE interrupt request if the SPTIE bit in the SPI control register is also
set.
NOTE
Do not write to the SPI data register unless SPTE is high.
During an SPTE interrupt, user software can clear SPTE by writing to the transmit data register.
1 = Transmit data register empty
0 = Transmit data register not empty
MODFEN — Mode Fault Enable Bit
This read/write bit, when set, allows the MODF flag to be set. If the MODF flag is set, clearing MODFEN
does not clear the MODF flag. If the SPI is enabled as a master and the MODFEN bit is 0, then the SS
pin is available as a general-purpose I/O.
If the MODFEN bit is 1, 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 15.7.4 SS (Slave Select).
If the MODFEN bit is 0, 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 15.3.6.2 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 15-3. SPR1 and
SPR0 have no effect in slave mode.
Table 15-3. SPI Master Baud Rate Selection
SPR1 and SPR0
00
01
10
11
Baud Rate Divisor (BD)
2
8
32
128
Use this formula to calculate the SPI baud rate:
Baud rate = ^BUSCLK
BD
MC68HC908QC16 • MC68HC908QC8 • MC68HC908QC4 Data Sheet, Rev. 3
Freescale Semiconductor
187