Datasheet

Data Sheet AD7923
Rev. D | Page 21 of 24
C
S
SCLK
DOUT
DIN
t
5
t
11
t
8
t
QUIET
t
CONVER
T
1 2
3 4 5 6 1
1
12
13
1
4 1
5 1
6
THREE-
STATE
ZERO
ADD1 ADD0
DB11
DB10 DB4
DB3 DB2
DB1 DB0
THREE-
STATE
2 IDENTIFICATION
BITS
ZERO
B
WRITE SEQ1 DONTC
DONTC
ADD1 ADD0 CODING DONTC DONTC DONTC DONTC
t
9
t
2
t
3
t
10
t
6
t
7
t
4
03086-027
Figure 27. Serial Interface Timing Diagram
CS
1 16 1 16 1 16
SCLK
VALID DATA
VALID DATA
DOUT
POWER-UP
DIN
t
CYCLE
5µs MIN
t
QUIET
MIN
03086-028
Figure 28. General Timing Diagram
MICROPROCESSOR INTERFACING
The serial interface on the AD7923 allows the part to be directly
connected to a range of many different microprocessors. This
section explains how to interface the AD7923 with some of the
more common microcontroller and DSP serial interface protocols.
AD7923-to-TMS320C541
The serial interface on the TMS320C541 uses a continuous
serial clock and frame synchronization signals to synchronize
the data transfer operations with peripheral devices like the
AD7923. The
CS
input allows easy interfacing between the
TMS320C541 and the AD7923 without any glue logic required.
The serial port of the TMS320C541 is set up to operate in burst
mode with internal CLKX0 (Tx serial clock on Serial Port 0)
and FSX0 (Tx frame sync from Serial Port 0). The serial port
control register (SPC) must have the following setup: FO = 0,
FSM = 1, MCM = 1, and TXM = 1. The connection diagram is
shown in Figure 29. It should be noted that for signal processing
applications, it is imperative that the frame synchronization
signal from the TMS320C541 provides equidistant sampling.
The V
DRIVE
pin of the AD7923 takes the same supply voltage as
the TMS320C541. This allows the ADC to operate at a higher
voltage than the serial interface, that is, the TMS320C541, if
necessary.
TMS320C541
1
AD7923
1
CLKX
CLKR
DR
DT
FSX
FSR
V
DD
SCLK
DOUT
DIN
C
S
1
ADDITIONAL PINS REMOVED FOR CLARITY.
03086-029
V
DRIVE
Figure 29. Interfacing to the TMS320C541
AD7923-to-ADSP-21xx
The ADSP-21xx family of DSPs is interfaced directly to the
AD7923 without any glue logic required. The V
DRIVE
pin of the
AD7923 takes the same supply voltage as the ADSP-218x,
which allows the ADC to operate at a higher voltage than the
serial interface, that is, ADSP-218x, if necessary.
The SPORT0 control register should be set up as follows:
TFSW = RFSW = 1, alternate framing
INVRFS = INVTFS = 1, active low frame signal
DTYPE = 00, right justify data
SLEN = 1111, 16-bit data-words
ISCLK = 1, internal serial clock
TFSR = RFSR = 1, frame every word
IRFS = 0
ITFS = 1