The SPI Function - The HCS12/9S12: An Introduction to Software and Hardware Interfacing - page 510

O0
to
O23

PWM
brightness
control

I SET

Current
source

LED
drivers

Divider/
counter
network

OSC

Row
multiplexer

Character-
generator
RAM

Character-
generator
ROM

Blink
speed
select

Blink

Configuration
register

RAM

CLK

CS
DIN
DOUT

Serial interface

Figure 10.26 ■ MAX6952 functional diagram

The upper 8 bits of the shift register select the destination register to which the lower 8 bits of
the shift register are to be transferred. The address map of the MAX6952 is shown in Table 10.9.
The procedure for writing the MAX6952 is as follows:
Step 1
Pull the CLK signal to low.
Step 2
Pull the CS signal to low to enable the internal 16-bit shift register.
Step 3
Shift in 16 bits of data from the DIN pin with the most significant bit first. The most
significant bit (D15) must be low for a write operation.
Step 4
Pull the CS signal to high.
Step 5
Pull the CLK signal to low.