Status Byte; Errors - Stanford Research Systems SR530 Manual

X n {,v}
n designates one of the 6 general purpose analog
ports located on the rear panel. If n is 1,2,3, or 4,
the X command will return the voltage on the
designated analog input port (X1-X4) in volts. If n
is 5 or 6, then v may also be sent. If v is included,
the designated analog output port (X5 or X6) will
be set to v volts where v has the range -10.238V
to +10.238V. If v is absent, the output value of the
selected port is returned. On power-up, port X5 is
the ratio output. An "X 5" command will read the
ratio output. An "X 5" command with the
parameter v will set port X5 to v volts, overriding
the ratio output. Port X5 will return to the ratio
output on power-up or reset.
Y {n}
The Y command reads the status byte. (See the
following section for a definition of the Status
Byte.) n designates one bit, 0-7, of the status
byte. If n is included, the designated bit of the
status byte is returned. The bit which is read is
then reset. If n is absent, the value of the entire
byte is returned and all status bits are then reset.
This status byte may also be read over the GPIB
using the serial poll command.
Z
The Z command causes an internal reset. All
settings return to the default values shown on
page 15. The ERR LED will be on for about three
seconds to indicate that the stored instrument
settings are being ignored. If the RS232 echo
mode is on, the sign-on message is sent over the
RS232 interface.

Status Byte

The SR530 maintains an 8-bit status register
which the user may read to obtain information on
the unit's status. The status byte may be read in
two ways: by sending the Y command, which
returns the value of the byte in ASCII coded
decimal, or, when using the GPIB, by performing a
serial poll. The returned status byte reflects all of
the status conditions which have occurred since
the last time the byte was read. After the status
byte has been read, it is cleared. Thus, the status
byte should be read initially to clear all previous
conditions (especially after a power up or after
settings have been changed).
The definitions for each bit of the status byte are
given below:
Bit 0
Not Used
Bit 1
Command Parameter Out of Range. This bit is
set if a parameter associated with a command is
not in the allowed range.
Bit 2
No Reference. This bit is set when no reference
input is detected, either because the amplitude is
too low or the frequency is out of range.
Bit 3
Unlock. This bit is set when the reference
oscillator is not locked to the reference input. If
there is no reference input, bit 2 (no reference) will
be set but bit 3 (unlock) may not be.
Bit 4
Overload. This bit is set if there is a signal
overload. This can happen when the sensitivity is
too high, the dynamic reserve is too low, the offset
is on, or the expand is on. Overloads on the
general purpose A/D inputs or the ratio output are
not detected.
Bit 5
Auto Offset Out of Range. This bit is set if the
auto offset function cannot zero the output
because the output exceeded 1.024X full scale.
Bit 6
SRQ. This bit is set if the SR530 has generated
an SRQ on the GPIB interface. This bit is reset
after the SR530 has been serial polled. This bit is
set only for status reads via a serial poll, ie., Bit 6
always zero for the RS232 .
Bit 7
Command Error. This bit is set when an illegal
command string is received.

Errors

Whenever a 'parameter out of range' or an
'unrecognized command' error occurs, the
appropriate status bits are set and the ERR LED
flashes. In addition, any commands remaining on
the current command line (up to the next <cr>) are
lost. The ERR LED will also light if any of the
internal communication buffers overflows. This
occurs when 240 characters are pending on the
command queue or output queue. The ERR LED
will go off as soon as all buffers drop below 200
24