1. 	Overview

DIGI96/8 PAD is in most items identical to DIGI96/8 PRO Rev. 2. That's why this addendum lists only differences and additions. For all basic information please read Internal Reference DIGI96 Series and DIGI96/8 PRO addendum.

Differences in hardware:

DIGI96/8 PAD adds an analog input, realized using a second stereo TRS jack. Two jumpers (J2/J3) on the board allow to change the input sensitivity between +4 dBu and -10 dBV. 

The first version of the PAD (revision 000 and 002) uses an AK5352 as AD-converter. Due to the clock situation on the board 64 kHz and 88.2 kHz were not supported for analog recordings. To avoid misfunction they have to be disabled in the driver. The output uses an AD1855.

The second version (revision 004) uses an AK5383. This chip allows to use all sample rates at the analog input. The output uses an AD1852, which has much better THD+N values and a different volume control range (14 bit instead of 12 bit). In case the volume control is supported different routines for both cards have to be implemented).

DIGI96/8 PST is exactly the same as DIGI96/8 PAD Rev. 4. The only difference is the missing XLR input.

2. Clock Control Analog In

AD-converters are extremely sensitive to high frequency interference. To achieve the highest Signal to Noise ratio the PAD should operate with the same clock at input and output.

Therefore the following technique should be used:

At active clock mode AutoSync the digital output should always use the same sample frequency as the analog input. Because the hardware can't clock itself to an analog input signal (as opposed to a digital input signal)  it will automatically enter clock mode Master. The only thing for the driver to do is to set the same sample frequency at the output as at the analog input.

At active clock mode Master record and playback of the card should operate totally independent. Therefore the driver does not automatically set the output sample frequency as in AutoSync mode.

3. PCI-ID and Revision ID PAD

Vendor ID 10EE (Xilinx), PCI device ID in configuration area (offset 2):

DIGI96/8 PAD (DevID = 3FC3h): Adds an analog input to the functionality of the 96/8 PRO.

The PCI revision ID in the configuration area (Offset 08h) contains a version number:

Digi96/8 PAD, first revision: 000

DIGI96/8 PAD, second revision: 002 (identical to 000)

DIGI96/8 PAD, third revision: 004 (AK5383, AD1852)

4. PCI-ID and Revision ID PST

The PST has the same PCI-ID as the DIGI96/8 PAD. Actually the PAD driver is totally identical and compatible, only the XLR input will not work (because it is not present at all). To differ between PAD and PST the PCI revision ID in the configuration area (Offset 08h) has to be read:

DIGI96/8 PST, first revision: 005 (AK5383, AD1852)

5. Register

Read the control register

Bit 22-21=dev_id       Device-ID: 11 = DIGI96/8 PAD

The control register can not be used to identify whether it's a PAD or a PST!

Write to the control register

Additional register (Offset 0x20004)

0	wsel	Clock Source for playback is an external clock signal (Word Clock In), when this bit is set. Same as in DIGI96 series.

New:

1	analog	Sets the input selector to "Analog". This bit has a higher priority as the other input selctor bits. inp_0 and inp_1 have no meaning in case Analog is set. 
	
2
3
4	freqad_0
freqad_1
freqad_2	Sets sample frequency for the analog input:
001 = 32000 Hz
010 = 44100 Hz
011 = 48000 Hz
111 = 96000 Hz
Other combinations are not allowed. The frequency bits
F<2...0> of the SPDIF receiver are meaningless when Analog is active.
	
5	PD2	Resets the A/D-converter (Power Down Mode). This bit has to be set only once, when booting the computer (first time load of the driver), because the hardware automatically resets the ADC in case the freqad bits and the analog bit are changed.
	
6	dac_en	("soft-mute-bit"):
0 = analog output muted (default)
1 = analog output active

When first time starting the driver this bit should be set permanently. Before doing this please reset the DAC using the already exisiting PD bit. When un-loading the driver (shutdown of the system) this bit should be set back to 0, to mute the analog output, and to avoid a pop/click when the power supply's voltages break down.
	
7
8
9	CLATCH
CCLK
CDATA	These bits are connected to the corresponding pins of the D/A-converter. These bits can be used to access internal registers of the DAC. The format of this Microprocessor interface is described in the AD1855 and AD1852 datasheet (available at www.analog.com). The Windows driver uses this port to realize a volume control with 60 dB range. These bits should remain on low level when not used!

Important note

When booting the computer the bits CLATCH, CCLK and CDATA are set to a random state. The DAC therefore is in an undefined state when the driver is loaded. Before setting dac_en the DAC has to be reset using PD!

Note: We recommend to implement the dac_en bit routines in general (for all cards), as unsupported bits don't cause errors in other cards as PRO and PAD.

5. Example for a configuration dialog

The picture below shows the DIGI96/8 PAD settings dialog of the Windows 98/NT driver, which is basically identical for all cards of the DIGI96 series.

Function block Analog Input

The field 'Input' includes 'Analog' as additional input choice. The search automatic in the Windows driver (AutoSelect) searches only the digital inputs for a valid signal.

The status window 'Input Status' shows as source 'Analog', mode 'Stereo', and the sample frequency used for the last recording. When controlling the hardware through the settings dialog (for example when monitoring the analog input with a headphone after setting 'Input') no record is done. Therefore a sample frequency has to be defined for the analog input. The driver should memorize the last sample frequency used  with the analog input and set this when analog input is activated. Of course this setting must be overwritten in case record starts.

The analog input does not support 64 and 88,2 kHz, these sample frequencies have to be disabled in the driver when using the analog input.

Function block Analog Output

Two sliders providing a nearly stepless analog volume control were added to the Windows driver. The control range is 0 to -60 dB. The precise amount of attenuation is shown as numerical value below the sliders. The sliders can be adjusted simultaneously by activating 'Couple'.

The DIGI96 series volume control using 6 dB steps is also available. When activating for example -6 dB this value will be added to the one of the slider, the actual attenuation will be displayed correctly below the faders as numerical value.

Function block Output

Due to the enhaced features of the XCS30 hardware the output options in the Windows driver were modified.

The field 'Output Format' shows two sections. The upper section sets the output format in relation to the input format. 'Automatic' and 'Force Adat' operate as usual. 'A/S Conv.' forces the output into SPDIF mode to realize an ADAT to SPDIF converter. This setting is overwritten when a multichannel playback is started.

The lower section includes all switches regarding the SPDIF output. Only 'Professional' was changed. If not active 'Consumer' format is set, making the extra switch 'Consumer' obsolete.

DIGI96/8 PST

Same as PAD, only XLR input disabled.