http://www.dd1us.de/Downloads/precise%20reference%20frequency%20rev%200_1.pdf
http://freqelec.com/pdf/rfs_12pg.pdf
http://www.mail-archive.com/time-nuts@febo.com/msg11134.html
http://www.analog.com/UploadedFiles/Data_Sheets/AD9830.pdf
http://www.dpie.com/pcmcia/rs232_pinout.gif
J2          Sipex SP233ACT
            T2IN  1  20 R2OUT
Pin 1 Vcc   T1IN  2  19 R2IN
Pin 2 Vcc   R1OUT 3  18 T2OUT
Pin 3 Rin---R1IN  4  17 V-
Pin 4 Tout--T1OUT 5  16 C2-
Pin 5 gnd---GND   6  15 C2+
            VCC   7  14 V+
	    C1+   8  13 C1-
	    GND   9  12 V-
	    C2-   10 11 C2+

Here is the pinout of the 9 pin connector:
PIN FUNCTION NOTES
J1-1 +15V DC power input
J1-2 GROUND Provides DC return, RS-232 return
J1-3 Loop Lock Indicator Indicates whether or
     not the output frequency is stabilized to
     the Rb atomic reference. Low output means
     it is locked. It should go low a few minutes
     after power up (it takes longer when the
     unit is cold).
J1-4 NOT USED
J1-5 GROUND Provides DC return, RS-232 return
J1-6 1 PPS output 1 pulse per second output signal
     When the DDS is set to 8,388,608Hz
J1-7 NOT USED
J1-8 RS-232 Rx
J1-9 RS-232 Tx
The parameters of the serial connection are:
9600 baud
8 bits
one stop bit
no parity
no flow control

6834682608 Hz.
http://tf.nist.gov/timefreq/general/pdf/461.pdf page 47
6834682608 / 136 = 50255019.1764706

6834682610.904324 / 136 = 50255019.1978259

Fout = (N    / 2^32) * Fref
N    = (Fout / Fref) * 2^32

SERIAL# 5227
R=50255056.078356Hz F=2ABB5041FFFFFFFF
15MHz=4C690453 10MHz=32F0AD8D 5MHz=197856C6

SERIAL# 30574
R=50255055.000000Hz F=2ABB50428DE01A00

----------------------------------------------------------------

I added a forth like input statement function processor. Based on
an old artical in Dr. Doobs Jurnal. The program was called BASFORTH.
This is convenient when changing and adjusting frequencies without
having to enter the complete frequency.
The forth like interpreter has many of the normal forth functions.
The first thing that happens is the number on top of the stack
starts out with the variable to be changed and normal arithmatic
can be applied to it. This same stuff can be applied to the other
numner input statements.

EXAMPLES:
That in () is what is on the top pf the stack.
(FREQ) 12345678 C/R                       Leaves 12345678Hz in the DDS.
(FREQ) 10000000 200000 + C/R (12000000)   Leaves 10.2MHz in the DDS.
(FREQ) 4 + C/R (FREQ + 4)                 Adds 4Hz to the frequency 
                                           that was in the DDS.
(FREQ) 1e3 - C/R (FREQ - 1000)            Adds 1KHz to the frequency 
                                           that was in the DDS.
(FREQ) 8388608 C/R (8388608)              Leaves 8288608Hz in the DDS.
(FREQ) 8.388608e6 C/R (8388608)           Leaves 8288608Hz in the DDS.
(FREQ) 2 23 ^ C/R (8388608)               Leaves 8288608Hz in the DDS.

And a complicated one:
(FREQ) RND 2E4 * 1E4 - + C/R (FREQ + RND) Adds a random number between
                                           +10000Hz and -10000Hz to
					    the frequency in the DDS.

FORTH LIKE COMMANDS:
 
R>D D>R                           Convert Radians to Degrees and back.

+ - * / ^ CUBE QUR SQUARE SQR     Arithmatic

= > < SGN                         Rrelational functions

ACC ACS ACT ASC ASN ATN           Trig Functions
COS COT CSC SEC SIN TAN

ABS EXP FIX INT INV LN LOG RND    Math Functions

S? .                              View the stack, print
                                   the top of the stack

DUP OVER 2OVER DROP LX SWAP       Stack operations

CLS BYE STOP                      Clear screen, Quit, and
                                   Basic stop functions

>R R> R@                          Return stack operations
 
BEGIN DO ELSE IF LOOP THEN UNTIL  Looping functions


0 1 2 PI RAD REF                  Constants

It's fairly easy to add new forth commands or constants,
just follow the examples in the program.