mc9s12xd256 Freescale Semiconductor, Inc, mc9s12xd256 Datasheet - Page 532

• Manufacturer Part Number: mc9s12xd256
• Description: Hcs12x Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Chapter 12 Serial Peripheral Interface (S12SPIV4)
Data reception is double buffered. Data is shifted serially into the SPI shift register during the transfer and
is transferred to the parallel SPI data register after the last bit is shifted in.
After the 16th (last) SCK edge:
Figure 12-11
CPOL = 0 and CPOL = 1. The diagram may be interpreted as a master or slave timing diagram because
the SCK, MISO, and MOSI pins are connected directly between the master and the slave. The MISO signal
is the output from the slave and the MOSI signal is the output from the master. The SS pin of the master
must be either high or reconfigured as a general-purpose output not affecting the SPI.
532
•
•
End of Idle State
SCK Edge Number
MSB first (LSBFE = 0):
SCK (CPOL = 0)
SCK (CPOL = 1)
SAMPLE I
MOSI/MISO
CHANGE O
CHANGE O
SEL SS (O)
Master only
SEL SS (I)
t
t
t
t
MOSI pin
MISO pin
LSB first (LSBFE = 1):
Data that was previously in the master SPI data register should now be in the slave data register and
the data that was in the slave data register should be in the master.
The SPIF flag in the SPI status register is set, indicating that the transfer is complete.
L
T
I
L
, t
= Minimum idling time between transfers (minimum SS high time)
= Minimum leading time before the first SCK edge
= Minimum trailing time after the last SCK edge
T
, and t
is a timing diagram of an SPI transfer where CPHA = 0. SCK waveforms are shown for
I
are guaranteed for the master mode and required for the slave mode.
t
L
MSB
LSB
1
Figure 12-11. SPI Clock Format 0 (CPHA = 0)
2
Begin
Bit 6
Bit 1
3
MC9S12XDP512 Data Sheet, Rev. 2.17
4
Bit 5
Bit 2
5
6
Bit 4
Bit 3
7
Transfer
8
Bit 3
Bit 4
9
10
Bit 2
Bit 5
11
12
Bit 1
Bit 6
13 14
End
MSB
LSB
15
16
Minimum 1/2 SCK
Freescale Semiconductor
t
T
for t
Begin of Idle State
T
t
, t
I
l
, t
L
t
L