Operation - Novatech 425A Instruction Manual

4.0

Operation

4.1 Power on reset. After power is applied, the
425A takes approximately 300 ms to perform its ini-
tialization sequence. Any communication during
this time will be ignored or may cause erroneous
operation.
4.2 Specifications are met within 15 minutes of
power-up in stable environment.
4.3 After the 425A has been installed in the cus-
tomer application system, all that is required for
operation is to send the appropriate data.
4.4 Serial commands are shown on the previous
page. The commands consist of a one or two charac-
ter alpha-numeric mnemonic separated from the
operand by a space. Some commands do not have an
operand, so the space is not necessary.
4.5 To facilitate use with various systems, the com-
mands can be terminated by a line feed (LF), car-
riage return (CR) or any combination.
4.6 The user host hardware must properly format
the asynchronous serial port data. Incorrect format-
ting will result in erroneous or erratic operation. See
Table 1 for Serial Error Codes. Not all error codes
are used in all versions.
Table 1: Serial Error Codes
Error Code
Good command received (not sent for
OK
?0
?1
?2
?3
?4
?5
?6
?7
?8
?f
4.7 If you are using an external clock, the frequency
value sent to the 425A command must be scaled.
NOVATECH INSTRUMENTS
Meaning
R, CLR and QUE)
Unrecognized Command
Bad Frequency
Bad AM Command
Input line too long
Bad Phase
Bad Time
Bad Mode
Bad Amp
Bad Constant
Bad Byte
4.8 The nominal Internal Clock has a value that pro-
duces a even step size of 10.0 Hz. Thus a scale fac-
tor is necessary to determine your exact output
frequency when using external clock sources. For
example, to obtain 10 MHz output when using a 10
MHz reference (940.0 MHz internal master clock),
your frequency setting would be:
F = F
setting desired
F = 9.98138215286
setting
send: F0 9.98138215286
4.9 When used with an external clock of 250 MHz
to 1000 MHz ("C e" command), your setting will
be given by:
F = F
setting desired
where F is your external clock in MHz.
clk
You must account for your external clock frequency
accuracy and calculation round-off when using an
external clock. Most calculators have less than 48-
bits of resolution.
The noise and accuracy specifications are directly
affected by the quality of the external source. Unless
care is exercised, your specifications may be
degraded. Please verify your system requirements
with the chosen clock mode.
4.10 For example, if you were using an OC-12
clock of 622.08 MHz, and desire a 10 MHz output,
your calculation will be:
F = F
setting desired
= 10.0*938.249922368853/622.08
= 15.08246402985
Send: F0 15.08246402985
4.11 Since the internal frequency resolution of the
425A is 48-bits, the typical fractional frequency
error (f/f) for output frequencies in the MHz range
will be on the order of 1x10
ues are not possible due the round-off from the
external clock scaling. For the example, the 10.00
MHz error will be approximately 2 Hz when using
an external 10 MHz clock, resulting in 2x10
5
*0.998138215286 MHz
*938.249922368853/(F
NOTE:
*938.249922368853/(F
-12
, even when exact val-
Rev 1.01, 425A Manual
) MHz
clk
) MHz
clk
-13
f/f.