Texas Instruments TMS320C3x - Manual (Page 425)

Serial Ports
12-46
12.2.14.5 Serial Analog-to-Digital (A/D) and Digital-to-Analog (D/A) Interface Example
The DSP201/2 and DSP101/2 family of D/As and A/Ds from Burr Brown also
offer a zero-glue-logic interface to the ’C3x family of DSPs. The interface is
shown in Example 12–7. This interface is used as an example of the ’C3x serial
port configuration and operation.
Example 12–7. TMS320C3x Zero-Glue-Logic Interface to Burr Brown A/D and D/A
± 2.75 V
±
2.75 V
+5 V +5 V CASC
XCLK
SINA
SINB
SYNC
SSF
SWL
CONV
VOUTA
VOUTB
± 3 V
±
3 V
Burr Brown DSP202 D/A Burr Brown DSP102 A/D
+5 V
+5 V
+5 V
CLKX0
DX0
FSX0
CLKR0
DR0
FSR0
CASC
XCLK
SOUTA
SYNC
SSF
CONV
VINA
VINB
1 M Ω
12.29 MHz
22 pF 22 pF
OSC0
OSC1
’C3x
TCLK0
The DSP102 A/D is interfaced to the ’C3x serial-port receive side; the DSP202
D/A is interfaced to the transmit side. The A/Ds and D/As are hard-wired to run
in cascade mode. In this mode, when the ’C3x initiates a convert command to
the A/D via the TCLK0 pin, both analog inputs are converted into two 16-bit
words, which are concatenated to form one 32-bit word.
1) The A/D signals the ’C3x via the A/D’s SYNC signal (connected to the
FSR0 pin) that serial data is to be transmitted.
2) The 32-bit word is then serially transmitted, MSB first, out the SOUTA serial
pin of the DSP102 to the DR0 pin of the ’C3x serial port.
3) The ’C3x is programmed to drive the analog interface bit clock from the
CLKX0 pin of the ’C3x.