Serial Peripheral Interface Module (SPI)

 

 

 

 

 

 

 

 

 

Addr.

Register Name

 

Bit 7

6

 

5

4

3

2

1

Bit 0

 

SPI Control Register

Read:

 

 

 

 

 

 

 

 

 

 

SPRIE

R

 

SPMSTR

CPOL

CPHA

SPWOM

SPE

SPTIE

 

 

 

$0044

(SPCR)

Write:

 

 

 

 

 

 

 

 

 

 

 

See page 211.

 

 

 

 

 

 

 

 

 

 

 

Reset:

0

0

 

1

0

1

0

0

0

 

 

 

 

 

 

 

 

 

 

 

 

 

SPI Status and Control

Read:

SPRF

ERRIE

 

OVRF

MODF

SPTE

MODFEN

SPR1

SPR0

 

 

 

 

 

 

 

$0045

Register (SPSCR)

Write:

R

 

R

R

R

 

 

 

 

 

 

See page 212.

 

 

 

 

 

 

 

 

 

 

 

Reset:

0

0

 

0

0

1

0

0

0

 

 

 

 

 

 

 

 

 

 

 

 

 

SPI Data Register

Read:

R7

R6

 

R5

R4

R3

R2

R1

R0

 

 

 

 

 

 

 

 

 

 

 

$0046

(SPDR)

Write:

T7

T6

 

T5

T4

T3

T2

T1

T0

 

See page 214.

 

 

 

 

 

 

 

 

 

 

 

Reset:

 

 

 

 

Unaffected by reset

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

R

= Reserved

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 15-3. SPI I/O Register Summary

15.4.1 Master Mode

The SPI operates in master mode when the SPI master bit, SPMSTR, is set.

NOTE

Configure the SPI modules as master or slave before enabling them. Enable the master SPI before enabling the slave SPI. Disable the slave SPI before disabling the master SPI. See 15.12.1 SPI Control Register.

Only a master SPI module can initiate transmissions. Software begins the transmission from a master SPI module by writing to the SPI data register. If the shift register is empty, the byte immediately transfers to the shift register, setting the SPI transmitter empty bit, SPTE. The byte begins shifting out on the MOSI pin under the control of the serial clock. See Figure 15-4.

MASTER MCU

 

SLAVE MCU

SHIFT REGISTER

MISO

MISO

 

 

 

MOSI

MOSI

 

 

SHIFT REGISTER

 

SPSCK

SPSCK

BAUD RATE

SS

SS

GENERATOR

 

VDD

Figure 15-4. Full-Duplex Master-Slave Connections

The SPR1 and SPR0 bits control the baud rate generator and determine the speed of the shift register. See 15.12.2 SPI Status and Control Register. Through the SPSCK pin, the baud-rate generator of the master also controls the shift register of the slave peripheral.

As the byte shifts out on the MOSI pin of the master, another byte shifts in from the slave on the master’s MISO pin. The transmission ends when the receiver full bit, SPRF, becomes set. At the same time that SPRF becomes set, the byte from the slave transfers to the receive data register. In normal operation,

MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1

198

Freescale Semiconductor

Page 197 Page 199
Page 198
Image 198
Freescale Semiconductor MC68HC908MR32, MC68HC908MR16 manual Master Mode, Serial Peripheral Interface Module SPI Addr
Page 197 Page 199

MC68HC908MR16, MC68HC908MR32 specifications

Freescale Semiconductor's MC68HC908MR32 and MC68HC908MR16 microcontrollers are part of the popular HC08 family, designed primarily for embedded applications. These microcontrollers are particularly favored in automotive, industrial, and consumer product sectors due to their reliability and versatility.

One of the standout features of the MC68HC908MR series is its CMOS technology, which enhances performance while minimizing power consumption. This makes these microcontrollers suitable for battery-operated devices. They operate at a maximum clock frequency of 2 MHz and offer a 16-bit architecture, providing a solid balance between processing power and efficiency.

The MC68HC908MR32 variant is equipped with 32KB of flash memory, which allows for the storage of complex programs and extensive data handling. In contrast, the MC68HC908MR16 features 16KB of flash memory, making it ideal for simpler applications. Both microcontrollers also come with 1KB of RAM, enabling efficient data processing and real-time operations.

Another significant characteristic of these microcontrollers is their integrated peripherals. They come with multiple input/output (I/O) pins, which allow for connectivity with various sensors and actuators. The built-in timer systems offer precise timing control for automotive and industrial applications, while the Analog-to-Digital Converter (ADC) provides essential conversion capabilities for various analog signals.

For communication purposes, the MC68HC908MR series includes a serial communication interface, enabling easy integration with other devices and systems. This versatility facilitates the development of complex systems that require interaction with external components.

Security is another crucial aspect of these microcontrollers. They have built-in fail-safe mechanisms to ensure reliable operation under various conditions, making them suitable for critical systems. Additionally, their robust architecture helps to safeguard against potential disruptions or attacks.

In summary, Freescale Semiconductor's MC68HC908MR32 and MC68HC908MR16 microcontrollers are key players in the embedded systems landscape. Their blend of power efficiency, integrated features, and scalability ensures they remain relevant for a wide array of applications, making them a favored choice among engineers and developers looking for dependable solutions in a competitive market.
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