Rainbow Electronics MAX1068 - Manual (Page 26)

DSP Interface
The DSP mode of the MAX1068 only operates in exter-
nal clock mode. Figure 23 shows a typical DSP interface
connection to the MAX1068. Use the same oscillator as
the DSP to provide the clock signal for the MAX1068.
The DSP provides the falling edge at CS to wake the
MAX1068. The MAX1068 detects the state of DSPR on
the falling edge of CS (Figure 17). Logic low at DSPR
places the MAX1068 in DSP mode. After the MAX1068
enters DSP mode, CS can be left low. A frame sync
pulse from the DSP to DSPR initiates a conversion. The
MAX1068 sends a frame sync pulse from DSPX to the
DSP signaling that the MSB is available at DOUT. Send
another frame sync pulse from the DSP to DSPR to
begin the next conversion. The MAX1068 does not
operate in scan mode when using DSP mode.
MAX1067/MAX1068
Multichannel, 14-Bit, 200ksps Analog-to-Digital
Converters
26 ______________________________________________________________________________________
DOUT*
CS
SCLK
1ST BYTE READ 2ND BYTE READ
*WHEN CS IS HIGH, DOUT = HIGH-Z MSB
HIGH-Z
3RD BYTE READ
LSB
S1 S0 D5 D4 D3 D2 D1 D0
24 20
16 12 8 6 4 1
D13 D12 D11 D10 D9 D8 D7 D6 0 0 0 0 0 0 0 0
Figure 22b. SPI Interface Timing with PIC16/PIC17 in Master Mode (CKE = 1, CKP = 0, SMP = 0, SSPM3 - SSPM0 = 0001)
SCK
SDI
GND
PIC16/17
I/O
SCLK
DOUT
CS
V
DD
V
DD
MAX1067
MAX1068
Figure 22a. SPI Interface Connection for a PIC16/PIC17
CONTROL BIT SETTINGS SYNCHRONOUS SERIAL-PORT STATUS REGISTER (SSPSTAT)
SMP BIT7 0
SPI Data-Input Sample Phase. Input data is sampled at the middle of
the data output time.
CKE BIT6 1
SPI Clock Edge-Select Bit. Data is transmitted on the rising edge of the
serial clock.
D/A BIT5 X Data Address Bit
P BIT4 X Stop Bit
S BIT3 X Start Bit
R/W BIT2 X Read/Write Bit Information
UA BIT1 X Update Address
BF BIT0 X Buffer-Full Status Bit
Table 8. Detailed SSPSTAT Register Contents
X = Don’t care.