The SPI Function - The HCS12/9S12: An Introduction to Software and Hardware Interfacing - page 517

HCS12

MAX6952 MAX6952

DOUT

DIN DOUT DIN

MOSI0

OSC

OSC

C SET

C SET

SCK0 CLK CLK

I SET

I SET

PM5

CS CS R SET

R SET

MISO0

Figure 10.30 ■ HCS12 driving two MAX6952s

Solution: The SPI0 module should be configured with the following features:
• 12-MHz baud rate
• Master mode with interrupts disabled
• Shift data on the rising edge with clock idle low
• Shift data out most significant bit first
• Disable mode fault
• Stop SPI0 on wait mode
Two MAX6952 chips should be configured as follows:

Intensity10 register
We set the intensity of both MAX6952s to maximum by sending out the following value:
0x01, 0xFF, 0x01, 0xFF
Sixteen bits need to be written to each MAX6952, of which the upper 8 bits are the address to
select the Intensity10 register.

Intensity32 register
Set the second and third displays to maximum intensity by sending the same data as to
Intensity10:
0x02, 0xFF, 0x02, 0xFF

Scan-limit register
Confi gure the MAX6952 to drive four monocolor displays by writing the following value to the
MAX6952:
0x03, 0x01, 0x03, 0x01 ; drive four displays

Configuration register
Confi gure this register to
• Select P1 blink phase
• Not to clear digit data on both plane P0 and P1