EMC12 ETC2 [List of Unclassifed Manufacturers], EMC12 Datasheet - Page 36

• Manufacturer Part Number: EMC12
• Description: Audio Interface for the EmPack System
• Manufacturer: ETC2 [List of Unclassifed Manufacturers]

Converting Levels from VME6U6-C12 to EMC12:
Controlling Individual Gain / Attenuation Components:
09 Jan 2006
The gain stages of the EMC12 Mezzanine were designed to provide a similar range of input and
output levels as the C12 Mezzanine for the VME6U6 boards. However, some differences
remain. Most notably, the EMC12 gain/attenuation settings are specified in decibels and the
VME6U6-C12 levels are specified as integer values used to set the digitally controlled voltage
dividers in its CODECs. There is also a different nominal full scale voltage reference; 2.8 Vp-p
for the EMC12 compared to 6.3 Vp-p for the VME6U6-C12.
These differences can be accommodated for with the following formulas to convert input and
output settings for the VME6U6-C12 to the decibel values for the EMC12. For both formulas,
value refers to the digital potentiometer values used for the VME6U6-C12 and dB refers to the
EMC12 values to be passed to the EmSetCodecLevels function.
Input level conversion:
Output level conversion:
The following functions in the EMAPI are available should you find it necessary to control the
various analog gain stages and signal paths separately. Please refer to the EmPack Software
Reference Manual for an explanation of the functions’ usage and arguments.
The functions below control the input signal path and gain stages; enabling the external –20 dB
attenuator, selecting the Mic or Line input to the CODEC, enabling the CODEC’s internal 20 dB
gain for the Mic input and the value of the CODEC’s register that sets its ADC gain.
int
EmSetCodecExtInputAtten (
)
int
EmSetCodecInputSel (
)
int
EmSetCodecMi cGain (
dB = 20 * log (value / 128) – 7.0
dB = 20 * log (value / (256 – value)) + 7.0
RESOURCE_HANDLE Resource,
BOOL ExtInputAtten
RESOURCE_HANDLE Resource,
int InputSel
RESOURCE_HANDLE Resource,
Communication Automation Corporation
EMC12 Hardware Reference Manual
int
EmGetCodecExtInputAtten (
)
int
EmGetCodecInputSel (
)
int
EmGetCodecMicGain (
RESOURCE_HANDLE Resource,
BOOL *ExtInputAtten
RESOURCE_HANDLE Resource,
int *InputSel
RESOURCE_HANDLE Resource,
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