Johnson DM3474, Руководство по обслуживанию

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PROGRAMMING
3-6
Part No. 001-3474-002
3.3 RECEIVE TO TRANSMIT SEQUENCE
Refer to Figure 3-5.
1. Synthesizer is loaded (B and A 24-Bit words or one long 32-bit A-Word).
2. The state of the 5RCL line does not have to be changed until the last bit is sent. However, RX will cease as soon
as it is changed.
3. The SYNTH ENABLE line should be held HIGH for 2 to 3 milliseconds after the last word is sent. This puts the
frequency synthesizer in a SPEEDUP MODE and slightly improves lock times.
4. After the last word is strobed in, 7 milliseconds (worst case) should elapse before 7.5 TX is turned ON. This
allows the synthesizer to come within 1 kHz of the desired frequency.
Figure 3-5 RX TO TX TIMING DIAGRAM
Dekey is a length of time to allow the TX to power down while the synthesizer is still in lock. This is needed
to meet ETSI (European Telecommunications Standards Institute) adjacent power specifications. Dekey is
approximately 3 ms in length. The 7.5 TX should be ramped or optimally filtered in such a way as to reduce the
Sinx/x power spreading. Speedup will slightly improve lock times and is 1 to 2 ms.