Problem SPI communication with AD1940


I make the prototype of active crossover with AD1940 and PIC18F67J60.

But I have  a problem that SPI communication between PIC18F67J60 and AD1940 during test prototype board.

I made test code for PIC18F67J60 that read core register (address 2642) but after running code, read data is 0x0000.

SPI configuration of PIC18F67J60 is as follows.

1) PIC18F67J60's SPI mode 3: SPI1CON.CKP = 1, SPI1STAT.SKE = 0; SPI1STAT.SMP =0;

2) SPI speed is set to FOSC/64 (FOSC = 25Mhz)

Behaviour of test code

1) set AD1940 SPI select pin to low.

2) write "READ (0x01)" command to SPI

3) read two bytes from SPI

4) set AD1940 SPI select pin to high.

When I probed CDATA signal of AD1940, there was no signal.

PS: AD1940 is work well with USBi, and also PIC18F67J60 is work well with other components (SPI SRAM, SPI EEPROM).

I don't know what's problem.

Is any one help me to solve this problem?