MC68HC12 Datasheet, PDF(293/478 Page) Motorola, Inc – The MC68HC912DT128A microcontroller unit (MCU) is a 16-bit device composed of standard on-chip peripherals including a 16-bit central processing unit

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MC68HC12 Datasheet, PDF (293/478 Pages) Motorola, Inc – The MC68HC912DT128A microcontroller unit (MCU) is a 16-bit device composed of standard on-chip peripherals including a 16-bit central processing unit

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Multiple Serial Interface

Serial Peripheral Interface (SPI)

Transfer

Begin

End

SCK (CPOL=0)

SCK (CPOL=1)

SAMPLE I

(MOSI/MISO)

CHANGE O

(MOSI pin)

CHANGE O

(MISO pin)

SEL SS (O)

(Master only)

SEL SS (I)

tL

MSB first (LSBF=0):

LSB first (LSBF=1):

MSB

LSB

Bit 6

Bit 1

Bit 5

Bit 2

Bit 4

Bit 3

Bit 4

Bit 2

Bit 5

Bit 1

Bit 6

tT tI tL

LSB Minimum 1/2 SCK

MSB

for tT, tl, tL

HC12 SPI CLOCK FORM 1

Figure 16-5. SPI Clock Format 1 (CPHA = 1)

16.5.3 SS Output

Available in master mode only, SS output is enabled with the SSOE bit

in the SP0CR1 register if the corresponding DDRS is set. The SS output

pin will be connected to the SS input pin of the external slave device. The

SS output automatically goes low for each transmission to select the

external device and it goes high during each idling state to deselect

external devices.

DDRS7

0

1

Table 16-3. SS Output Selection

SSOE

0

1

0

1

Master Mode

SS Input with MODF Feature

Reserved

General-Purpose Output

SS Output

Slave Mode

SS Input

MC68HC912DT128A â Rev 4.0

MOTOROLA

Multiple Serial Interface

Technical Data

293

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