s908qc16vdse Freescale Semiconductor, Inc, s908qc16vdse Datasheet - Page 187

• Manufacturer Part Number: s908qc16vdse
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

SPTE — SPI Transmitter Empty Bit
MODFEN — Mode Fault Enable Bit
SPR1 and SPR0 — SPI Baud Rate Select Bits
Freescale Semiconductor
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.
During an SPTE interrupt, user software can clear SPTE by writing to the transmit data register.
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
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
Fault Error.
In master mode, these read/write bits select one of four baud rates as shown in
SPR0 have no effect in slave mode.
Use this formula to calculate the SPI baud rate:
1 = Transmit data register empty
0 = Transmit data register not empty
15.7.4 SS (Slave Select).
Do not write to the SPI data register unless SPTE is high.
MC68HC908QC16 • MC68HC908QC8 • MC68HC908QC4 Data Sheet, Rev. 4
Table 15-3. SPI Master Baud Rate Selection
SPR1 and SPR0
00
01
10
11
Baud rate =
NOTE
BUSCLK
Baud Rate Divisor (BD)
BD
128
32
2
8
Table
15-3. SPR1 and
15.3.6.2 Mode
Registers
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