Belden Grass Valley NV8900, User Manual

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15
NV8900
User’s Guide
Some of the MADI interfaces use DB25 connectors. You can obtain DB25 breakout
cables from Grass Valley or build your own cables. (The Grass Valley part number is
WC0053. The sales order code is NV5000-CABLE1.)
Obtaining Software and Documentation
This document is available through the Grass Valley web site.
Maintenance
The NV8900 requires no maintenance.
Channel Numbering
The MADI interfaces support 64 audio channels, 0–63. The MADI channels are paired on the
AES inputs or outputs.
Use the following formula to calculate a port number, given a MADI channel number:
p =

m / 2

+ 1 0
≤
m
≤
63.
Use the following formulas to calculate a MADI channel pair, given a port number:
m
1
= p × 2 – 2 1
≤
p
≤
32.
m
2
= p × 2 – 1
Audio Rates
According to the MADI specification, MADI receivers and drivers operate at 125 MHz which
supports 100M bits per second under 4B5B encoding. The receivers expect and the drivers
produce 64 audio channels at exactly 48
kHz. The 64 channels consume 98,304,000 bps
with a 1.7% margin for sync symbols and padding.
At least one sync symbol must accompany every MADI frame. The minimal number of sync
symbols is 48,000 per second. At 10 bits per symbol, that is 480,000 bits out of 2,120,000
spare bits.
The AES10-2003 specification’s tolerance on the transmission rate is 100 ppm (10
–4
). Thus
the rate must be 125 MHz ± 12,500 kHz.
 Our MADI interfaces send and receive AES at 48.0 kHz exactly. The data rate is, of course,
affected by the actual transmission rate. The effect on a 48 kHz data rate is a variance of
± 4.8 Hz.