Texas Instruments DEM-PCM1717 - Manual (Page 9)

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DEM-PCM1717
HARDWARE CONNECTIONS FOR THE
DEM-DAI1717
Hardware configuration of the DEM-DAI1717 evaluation
board consists of supplying a source of digital audio data,
connecting the board to an IBM-PC parallel port, connecting
the audio output to a speaker or measurement tool and
supplying a source of power to the system board.
Digital Audio Source
Figure 11 shows the “schematic” drawing of the DEM-
DAI1717 evaluation board. There are a total of four connec-
tors that must be used for the PCM1717 to reproduce digital
audio data. Figure 12 details the parts location and orienta-
tion for the DEM-DAI1717 evaluation board. The PCB
layer design for the traces and ground planes used in the
DEM-DAI1717 system board are shown in Figure 13.
Digital Audio Input Data
The source of digital audio data is connected via the coax
connector labeled as “CN3” or “COAX.” This port is used
if the SPDIF digital audio data comes from a RCA connec-
tor.
SPDIF data can also be provided to the DEM-DAI1717
system board via fiber optic connection. The “port” that is
used for this form of data is connected to the U4 or OPT
connection. The connection is made using a standard
“Toslink” connector.
Power Connections
A 5 pin connector labeled CN1 is used to connect power to
the DEM-DAI1717. A separate +5V supply is used for the
SPDIF receiver chip and the PCM1717, labeled as +V
CC
.
The power connections +V
S
and –V
S
are used to provide for
the active filter op-amp, OPA2604. This amplifier should
not be run at power supply voltages greater than
±
15V. The
remaining pins are used for ground connections. These
grounds are not isolated from each other electrically.
Analog or Audio Connections
The analog outputs of the PCM1717 are brought out directly
through RCA jacks CN6 and CN7 for the left and right
channel respectively. These outputs are referred to 1/2 of the
V
CC
voltage, i.e. the output swings symmetrically about
2.5V for a 5V supply.
SOFTWARE DESCRIPTION
The PCM1717 demo software is used to control the internal
register settings of the PCM1717 through a set of four
windows. The main menu is brought up by clicking on the
“D17CTRMK” icon in the applications folder.
MAIN MENU
Figure 14 shows the main menu that is brought up when the
“D17CTRMK” icon is selected. This menu has three areas
of interest. The “Execute” option allows the user to either
reset the PCM1717 to its default power-on state using the
Reset command, or allows the user to exit from the PCM1717
software. The execute menu can be opened by either click-
ing on the “Execute” or by using the Alt-E key sequence.
(All of the menus and commands can be activated by using
the mouse and the left button or Alt key sequences). The
Windows submenu (Alt-W) allows the Attenuation (Alt-A),
Function (Alt-F), and Dataform (Alt-D) submenus to be
opened. The function of these menus is explained in the next
section.
The bottom of the PCM1717 Main or Control Menu con-
tains the Hexadecimal value of the current contents of the
PCM1717 four control or Mode Registers. For a more
detailed description of these registers consult the product
data sheet for the PCM1717E audio digital-to-analog con-
verter.
A Pass/Hold selection is available for all three of these
control menus. When the Menu is in the Pass mode then
commands are sent to the PCM1717 as various selection or
options are selected immediately. When the Menu is in the
Hold mode the changes are held in the software for the
DEM-PCM1717 until the menu is changed to the Pass
Mode.
ATTENUATE MENU
The PCM1717 allows the user to command 255 steps of
noiseless attenuation into each channel. The left and right
channels can either be controlled together, i.e. equal attenu-
ation of both channels, or independent control over each
channel. Figure 15 shows the attenuation menu.
To change the attenuation or volume of a channel use the
mouse pointer over the bar in the attenuation level menu for
the desired channel, press and hold the left button and drag
the bar to the desired level. Pressing the Hold selection in the
Control Data section of the Attenuation Control Menu will
change the Hold section to Pass, and the necessary register
settings for the desired attenuation level will be passed to the
PCM1717. The level or volume will change. (Note that if the
Left and Right channels have been chosen to be equal from
the Format Control menu, then only the Left channel Attenu-
ation Level will be selectable.)
FORMAT CONTROL MENU
This menu allows the user to program the data input format,
resolution, Left-Right clock polarity, output format, and
Attenuation formats for the PCM1717. This menu is com-
posed of six submenus explained below. Figure 16 shows
the default menu for this section.
FORMAT
This menu allows the PCM1717 to be programmed for
either the standard or I
2 S format for incoming data to the
DAC. The standard format is used when the incoming data
is MSB aligned to the Left-Right clock or LRCK. The I
2 S
format is used when the incoming data conforms the Inter-
IC sound format. Refer to the product data sheet of the