Datum Systems PSM-500L Manual do Utilizador descarregar pdf (Página 7)

Datum Systems, Inc. PSM-500 Modem Remote Control Protocol

Rev 0.93 12/12/10

B-7

Bytes 24-25 – A2 FE hex – AUPC Min Cxr Level. (FE A2 Hex = -35.0 in 0.1dB steps)

Bytes 26-35 – 00 00 00 00 hex – Spare

Packet Ending – “96 C0”

Several things should be noticed here. First, the Write Enable flags do not always cover the enable change

for all of the Write bit flags themselves, therefore the Carrier Enable must be repeated from the previous

response or set for this specific case. Second, a value for the transmit output level, AUPC levels, etc was

used although it was not necessary. This could have been all zeros since the enable flag did not enable

setting this parameter.

3. Read the response from the modem showing the correctly set transmit frequency.

The response will look the same as the original request command except that the frequency change flag

should be set and the data bytes for the frequency should now read “60 19 73 04” hex – meaning the

Frequency = 74.652000 MHz

The response status byte is shown as “76” hex, and the error byte was taken as “00”. The “76” status byte

means Alarm A and B is active, and the Unit, Mod and Demod is in alarm. That was because the modem

has no Data or IF connections. These status bits will change depending on other factors in the modem.

Following is an abbreviated list of currently available commands and the parameters monitored and/or

controlled by that command. Click on the underlined “Command Byte” to jump to that command table.

Far End Modem Control via the MCC and M5 Compatibility

The M5 and the M500 series protocols contain the ability to relay control packets and responses via the

Modem Control Channel, or MCC, from a local to a single far end modem. The PSM-500 modem can

interoperate with the previous generation of M5 modem series, the PSM-4900. To aid in mixed systems

containing both M500 and M5 series modems the M500 series has almost complete M5 series protocol

capabilities. This exists side by side with the newer protocols described in this addendum, but are limited

naturally to the capabilities of the M5 series. For further information on the M5 series protocol, please see

the M5 Appendix B available on the web site.

As noted before the M5 series of protocols use a “Mode” byte value of “1” to indicate a local packet, and a

value of 2 to indicate a far end packet. The M500 series uses a value of “5” for local and “6” for far end

packets. Far end packets look just like local packets in all other respects, including the use of the local

modem’s address. When a modem receives a valid control packet with a mode byte value of 6 (M500) or 2

(M5) then it retransmits that packet to the far end modem via the MCC. You must use the local modem’s

address in the packet or it will be rejected.

M500 series protocol compatibility with the M5 series extends to the use of the Modem Control Channel to

send and receive far end packets. That means that a local M500 series modem can be set up to link to and

control either another M500 modem or an M5 series modem at the far end. The M500 series has a built in

multiplexer, but the multiplexer is an option in the M5 series. See the respective manuals for information

on setting up the link and multiplexers to allow this type of control. The following link packet protocols can

be used.

MCC Channel Far End Control Modes

Controller

End Modem

Far End

Modem

Mode

Byte

Possible?

M500

Yes

M500

Yes

M500

Yes

M500

Yes

M500

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