AN2320 Freescale Semiconductor / Motorola, AN2320 Datasheet - Page 5

• Manufacturer Part Number: AN2320
• Description: Interfacing the MCF5272 to a Standalone CAN Controller
• Manufacturer: Freescale Semiconductor / Motorola

2.1
The MCF5272 QSPI module provides a glueless SPI interface to the 82C900’s synchronous serial channel
(SSC). The QSPI and SSC hardware interfaces are detailed here.
2.1.1
The QSPI module on the MCF5272 provides a serial peripheral interface with queued transfer capability,
which allows up to 16 data transfers with no CPU intervention. The QSPI interface will support data
transfers, msb first, of anywhere between 8 and 16 bits. It will support baud rates from 129.4Kbps up to 16
MBps and can be interfaced to a maximum of 15 devices using the four peripheral chip-select lines.
The module has a total of seven signals: QSPI_Dout, which is the serial data output from the QSPI module,
QSPI_Din, which is the serial data input to the QSPI module, QSPI_CLK, which is the QSPI clock output,
and QSPI_CS[0:3], which are the four peripheral chip-select output signals. Four signals are used to
interface to the 82C900: QSPI_Dout, QSPI_Din, QSPI_CLK and QSPI_CS0.
The clock phase, clock polarity, chip select active logic level, and delays before and after transfer
highlighted in Figure 3 are all programmable via the QSPI registers. This flexibility in clocking and data
transfer eliminates the need for additional glue logic to meet the 82C900 timing requirements or to
accommodate the polarity and phase of its clock, which are internally configured. The data transfer baud
rate is also programmable; this is explained in more detail in Section 2.2, “Clocking.”
MOTOROLA
SPI Interface
MCF5272 QSPI Module
+3.3V
Charge Pump
MAX682
GND
Interfacing the MCF5272 to a Standalone CAN Controller
Freescale Semiconductor, Inc.
+5V
For More Information On This Product,
Figure 2. CAN Daughter-Card Circuitry
24MHz Clock
ACT1100
Go to: www.freescale.com
CAN Transceiver
PCA82C250
CAN Controller
CAN Transceiver
82C900
PCA82C250
P[0..7]
CANH
CANL
SPI Interface
5