MC68HC711D3CFNE2 Datasheet, PDF (85/124 Pages) Freescale Semiconductor, Inc – Power Saving STOP and WAIT Modes

Freescale Semiconductor, Inc.
8.5.2 Serial Peripheral Status
SPSR — Serial Peripheral Status Register
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Bit 7
6
5
4
3
2
1
Bit 0
SPIF
WCOL
0
MODF
0
0
0
0
RESET:
0
0
0
0
0
0
0
0
SPIF — SPI Transfer Complete Flag
SPIF is set upon completion of data transfer between the processor and the external
device. If SPIF goes high, and if SPIE is set, a serial peripheral interrupt is generated.
To clear the SPIF bit, read the SPSR with SPIF set, then access the SPDR. Unless
SPSR is read (with SPIF set) first, attempts to write SPDR are inhibited.
WCOL — Write Collision
Clearing the WCOL bit is accomplished by reading the SPSR (with WCOL set) fol-
lowed by an access of SPDR. Refer to 8.3.4 Slave Select and 8.4 SPI System Errors.
0 = No write collision
1 = Write collision
Bit 5 — Not implemented
Always reads zero
MODF — Mode Fault
To clear the MODF bit, read the SPSR (with MODF set), then write to the SPCR. Refer
to 8.3.4 Slave Select and 8.4 SPI System Errors.
0 = No mode fault
1 = Mode fault
Bits [3:0] — Not implemented
Always read zero
8.5.3 Serial Peripheral Data I/O
The SPDR is used when transmitting or receiving data on the serial bus. Only a write
to this register initiates transmission or reception of a byte, and this only occurs in the
master device. At the completion of transferring a byte of data, the SPIF status bit is
set in both the master and slave devices.
A read of the SPDR is actually a read of a buffer. To prevent an overrun and the loss
of the byte that caused the overrun, the first SPIF must be cleared by the time a second
transfer of data from the shift register to the read buffer is initiated.
SPDR — SPI Data Register
Bit 7
6
5
4
3
2
Bit 7
6
5
4
3
2
NOTE
SPI is double buffered in and single buffered out.
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1
Bit 0
1
Bit 0
SERIAL PERIPHERAL INTERFACE
TECHNICAL DATA
8-7
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