MC68HC08AS32 Datasheet, PDF (224/280 Pages) Motorola, Inc – M68HC08 Family of 8-bit microcontroller units (MCUs)

NOTE:
OVRF — Overflow Bit
This clearable, read-only flag is set if software does not read the byte in the
receive data register before the next byte enters the shift register. In an overflow
condition, the byte already in the receive data register is unaffected, and the
byte that shifted in last is lost. Clear the OVRF bit by reading the SPI status and
control register with OVRF set and then reading the SPI data register. Reset
clears the OVRF flag.
1 = Overflow
0 = No overflow
MODF — Mode Fault Bit
This clearable, ready-only flag is set in a slave SPI if the SS pin goes high during
a transmission. In a master SPI, the MODF flag is set if the SS pin goes low at
any time. Clear the MODF bit by reading the SPI status and control register with
MODF set and then writing to the SPI control register. Reset clears the MODF
bit.
1 = SS pin at inappropriate logic level
0 = SS pin at appropriate logic level
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 CPU interrupt
request if the SPTIE bit in the SPI control register is set also.
Do not write to the SPI data register unless the SPTE bit is high.
For an idle master or idle slave that has no data loaded into its transmit buffer,
the SPTE will be set again within two bus cycles since the transmit buffer
empties into the shift register. This allows the user to queue up a 16-bit value to
send. For an already active slave, the load of the shift register cannot occur until
the transmission is completed. This implies that a back-to-back write to the
transmit data register is not possible. The SPTE indicates when the next write
can occur. Reset sets the SPTE bit.
1 = Transmit data register empty
0 = Transmit data register not empty
MODFEN — Mode Fault Enable Bit
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 14.12.4 SS
(Slave Select).)
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 14.6.2 Mode Fault Error.)
Data Sheet
224
MC68HC08AS32 — Rev. 4.1
Freescale Semiconductor