Datasheet

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TLV5639 INTERFACED to TMS320C203 DSP
HARDWARE INTERFACE
A2
A3
A4
A6
IS
D(0–11)
5 V
A
B
C
G1
G2A
G2B
CS
D(0–11)
Y1
WE
REF
To Other Devices Requiring
Voltage Reference
OUT
LDAC
WE
R
LOAD
TMS320C203 74AC138
TLV5639
12
REG
A0
SOFTWARE
TLV5639C
TLV5639I
SLAS189C – MARCH 1999 – REVISED JANUARY 2004
Figure 13 shows an example of the connection between the TLV5639 and the TMS320C203 DSP. The only
other device that is needed in addition to the DSP and the DAC is the 74AC138 address decoding circuit . Using
this configuration, the DAC data is at address 0x0084 and the DAC control word is at address 0x0085 within the
I/O memory space of the TMS320C203.
LDAC is tied low so that the output voltage is updated on the rising WE edge.
Figure 13. TLV5639 to TMS320C203 DSP Interface Connection
Writing data or control information to the TLV5639 is done using a single command. For example, the line of
code which reads:
out 62h, dac_ctrl
writes the contents of address 0x0062 to the I/O address equated to dac_ctrl (0x0085, the address where the
DAC control register has been mapped).
The following code shows how to set the DAC up to use the internal reference and operate in FAST mode by a
write to the control register. Timer interrupts are then enabled and repeatedly generated every 205 µs to provide
a timebase for synchronizing the waveform generation. In this example, the waveform is generated by simply
incrementing a counter and outputting the counter value to the DAC data word once every timer interrupt. This
results in a saw waveform.
13