mc9s08qg8 Freescale Semiconductor, Inc, mc9s08qg8 Datasheet - Page 224

• Manufacturer Part Number: mc9s08qg8
• Description: Hcs08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Serial Peripheral Interface (S08SPIV3)
the end of the eighth bit time of the transfer. The SS IN waveform applies to the slave select input of a
slave.
When CPHA = 0, the slave begins to drive its MISO output with the first data bit value (MSB or LSB
depending on LSBFE) when SS goes to active low. The first SPSCK edge causes both the master and the
slave to sample the data bit values on their MISO and MOSI inputs, respectively. At the second SPSCK
edge, the SPI shifter shifts one bit position which shifts in the bit value that was just sampled and shifts the
second data bit value out the other end of the shifter to the MOSI and MISO outputs of the master and
slave, respectively. When CPHA = 0, the slave’s SS input must go to its inactive high level between
transfers.
15.4.2
There are three flag bits, two interrupt mask bits, and one interrupt vector associated with the SPI system.
The SPI interrupt enable mask (SPIE) enables interrupts from the SPI receiver full flag (SPRF) and mode
fault flag (MODF). The SPI transmit interrupt enable mask (SPTIE) enables interrupts from the SPI
transmit buffer empty flag (SPTEF). When one of the flag bits is set, and the associated interrupt mask bit
is set, a hardware interrupt request is sent to the CPU. If the interrupt mask bits are cleared, software can
poll the associated flag bits instead of using interrupts. The SPI interrupt service routine (ISR) should
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(MISO OR MOSI)
(MASTER OUT)
(REFERENCE)
(SLAVE OUT)
SAMPLE IN
MSB FIRST
BIT TIME #
(CPOL = 0)
(CPOL = 1)
LSB FIRST
(MASTER)
(SLAVE)
SS OUT
SPSCK
SPSCK
SS IN
MOSI
MISO
SPI Interrupts
BIT 7
BIT 0
1
MC9S08QG8 and MC9S08QG4 Data Sheet, Rev. 1.01
Figure 15-11. SPI Clock Formats (CPHA = 0)
BIT 6
BIT 1
2
...
...
...
BIT 2
BIT 5
6
BIT 1
BIT 6
7
BIT 0
BIT 7
8
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