AVM AVM RS232, Руководство пользователя

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AVM RS232 Programming — Crosspoint Messages (Class 2)
AVM RS232 Programming — Crosspoint Messages (Class 2)
Slew Rate
Slew rate examples:
1) You want audio to slew at a rate set by an FRC time of 6000 (a full range change of 6
seconds). Use the formula above with 6000 in place of FRC: 32640 ÷ 6000 = 5.44. The slew
rate to program is 5. This number must be transmitted as a 2 byte hex number. The high byte
is 00h and the low byte is 05h. When these two bytes are transmitted as slew rate parameters,
the outputs will slew at the desired rate.
2) You want a fast slew. Select a full range change value of 2 seconds (FRC time =
2000). 32640 ÷ 2000 = 16. The two bytes of the slew rate are 00h and 10h.
3) A very fast slew is FRC time = 100 (.1 seconds). the two bytes are 01h and 46h.
This is useful for “rounding off the corners” of audio changes.
4) You want a slow slew rate. Select an FRC time of 12000 (a full range change of 12
seconds). Using the formula you obtain: 32640 ÷ 12000 = 2.72. Use 3. The high byte is 00h
and the low byte is 03h.
5) You want a very slow slew rate. Select a slew rate of 1. The two bytes are 00h and
01h. This corresponds to an FRC time of 32 seconds.
The inverse of ramp time is slew rate which is expressed in units of steps/128
milliseconds. The slew rate determines how fast volume changes will take place. Regardless
of the current or target volume levels, any change in output volume will take place at the slew rate.
The advantage of using slew rate instead of ramp time, is that the volume of the output being slewed
rises at a steady rate that is independent of the distance traversed by the slew.
Calculating a slew rate:
The slew rate is a 2 byte hexadecimal number. You calculate a slew rate based on how fast in milli-
seconds (.001 second) you want the volume to go from full off to full on. This number (the FRC for
full range change) will be in the range 1-32,640. It sets the rate at which all audio changes (not just
full off to full on). The smaller the FRC time time, the faster the volumes will change. Typical FRC
time’s are in the neighborhood of 5000 (a full range change time of 5 seconds). For a fast rate of
change the FRC time should be small, e.g. in the range of 1000. For a slow rate of change the FRC
time should be around 10,000. Your chosen FRC time is then used to calculate the actual slew rate
value as follows:
Slew Rate = 32,640 ÷ FRC time