1250 Frequency Response Analyzer The RS423 and GPIB Ports. Remote Control
AMK/1250/4 13-27
13.14 LEARNT PROGRAMS. EXTERNAL STORING AND
RELOADING
Learnt programs may be transferred from the 1250 to an external device, via the RS423
port or the GPIB interface. These programs, if stored externally, can then he loaded
back into the 1250 at a later date. This greatly increases the number of programs that
can he learnt, although the 1250 can still only hold up to 18 of them at a time; programs
1 to 9 in 'Normal' memory and programs 10 to 18 in 'supervisor' memory.
The transfer is achieved by external command only; it cannot he commanded from the
front panel.
The setting of the DATA OUTPUT key is immaterial.
By using the relevant Commands listed in section 13.7, Learnt programs can be
compiled entirely on an external device and then transferred complete to the 1250.
All external Learnt program manipulations can be performed whilst the 1250 is making
measurements, but Commands to Execute Program will not be implemented until the
measurement is complete.
In the following examples, n = the Learnt Program number, from 1 to 18.
13.14.1 RS423 PORT, DEVICE CONTROL CHARACTERS
When Learnt Programs are transferred via the RS423 port, the 1250 automatically
generates four ASCII Device Control Characters. The user must ensure that any
external device used for recording and replaying Learnt Programs is compatible with
these characters. The four characters are:
Character Assigned Meaning
DC1 Turn Replay On
DC2 Turn Record On
DC3 Turn Replay Off
DC4 Turn Record Off
The original definition of the Device Control Characters is in: USA Standard Code for
Information Interchange (ASCII) X3.4 1968. It is further explained in:
British Standard 4730: 1974 Section 5.3
and: CCITT Volume VIII. 1 Recommendation V3 "International Alphabet No.5".
Example. The four characters are used with a cassette recorder as follows:
When the Command *Pn (List Program) is sent from the external device via the RS423
port, the 1250 replies with DC2 (Turn Record On), followed by the Learnt Program
contents which are then stored on the tape. When the final Program instruction *Q
(Quit) is detected, the 1250 first generates DC3 (Turn Replay Off), which is recorded on
the tape, then finally DC4 (Turn Record Off) which terminates the recording.
To load the Learnt program back into the 1250, the command *Ln is first sent from the
external device. The 1250 will respond with DC1 (Turn Replay On). The program will
then be transferred from the cassette up to the final *Q instruction followed by the pre-
recorded DC3 (Turn Replay Off), which terminates the Replay.
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