Racal Instruments

Model 2461C and 2251A Command Cross Reference

Racal Instruments has discontinued production of all 2251 and 2251A counters. The new Model 2461C Counter is our closest replacement for this counter. A command cross-reference guide is presented below to compare the command sets of these two counters. The key difference is that the 2461C uses a SCPI command set, while the 2251 and 2251A both use a native command set.

Our experience has seen many smooth transitions between the older 2251 products and the new 2461C. To help with this transition, a specification cross-reference guide has been developed to show how 2251 and 2461C specifications differ.

If you need additional compatibility information, please contact Racal Instruments Product Marketing.

2251 Command	Equivalent 2461C Command(s)	Comments
A0	Default state of 2461C	Selects front panel Input A
A1	Not implemented on 2461C	Selects SUMBUS Input A signal source
A2	Not implemented on 2461C	Connects timebase reference to Input A
AAC	INP1:COUP AC	Selects Input A AC coupling
AAD	INP1:ATT X1	Disables Input A x10 Attenuator
AAE	INP1:ATT X10	Enables Input A x10 Attenuator
AAU	INP1:COMP:AUTO ON	Selects Input A autotrigger mode
ADC	INP1:COUP DC	Selects Input A DC coupling
AE	SENS:AVER ON	Enables Averaging mode, 100 samples
AFD	INP1:FILT OFF	Disables Input A Low Pass Filter
AFE	INP1:FILT ON	Enables Input A Low Pass Filter
AHI	INP1:IMP 1M	Sets Input A input impedance to 1Meg ohm
ALI	INP1:IMP 50	Sets Input A input impedance to 50 ohms
AMN	INP1:COMP:AUTO OFF	Selects Input A Manual Trigger Mode
ANS	INP1:COMP:SLOP NEG	Sets Input A Trigger to Negative Slope
APS	INP1:COMP:SLOP POS	Sets Input A trigger to Positivie Slope
B0	SOUR:ROSC CLK10	Selects 10 MHz signal from backplane as reference frequency
B1	SOUR:ROSC EXT	Selects EXT STD. INPUT as reference frequency
BAC	INP2:COUP AC	Selects Input B AC coupling
BAD	INP2:ATT X1	Disables Input B x10 attenuator
BAE	INP2:ATT X10	Enables Input B x10 Attenuator
BAU	INP2:COMP:AUTO ON	Selects Input B autotrigger mode
BCC	INP:ROUT COMM	Selects Input A and B "common" mode
BCS	INP:ROUT SEP	Selects Input A and B "separate" mode
BDC	INP2:COUP DC	Selects Input B DC coupling
BHI	INP2:IMP 1M	Sets Input B input impedance to 1Meg ohm
BLI	INP2:IMP 50	Sets Input B input impedance to 50 ohms
BMN	INP2:COMP:AUTO OFF	Selects Input B Manual Trigger Mode
BNS	INP2:COMP:SLOP NEG	Sets Input B Trigger to Negative Slope
BPS	INP2:COMP:SLOP POS	Sets Input B trigger to Positivie Slope
CK	CONF:CHECk	Selects CHECK mode
D0	OUTP:TTLT0 ON	Enable Gate out signal on TTLTRG0
D1	OUTP:TTLT1 ON	Enable Gate out signal on TTLTRG1
D2	OUTP:TTLT2 ON	Enable Gate out signal on TTLTRG2
D3	OUTP:TTLT3 ON	Enable Gate out signal on TTLTRG3
D4	OUTP:TTLT4 ON	Enable Gate out signal on TTLTRG4
D5	OUTP:TTLT5 ON	Enable Gate out signal on TTLTRG5
D6	OUTP:TTLT6 ON	Enable Gate out signal on TTLTRG6
D7	OUTP:TTLT7 ON	Enable Gate out signal on TTLTRG7
D8	OUTP:TTLT0-7 OFF	Disable Gate output (default)
DD	TINT:DEL:TIME:STAT OFF	Disables Time Interval Delay
DE	TINT:DEL:TIME:STAT ON	Enables Time Interval Delay
FA	CONF1:FREQ	Selects Frequency A measurement mode
FB	CONF2:FREQ	Selects Frequency B measurement mode
FC	CONF3:FREQ	Selects Frequency C measurement mode
FT	CONF1:FTIM	Selects Fall Time A measurement mode
IP	RES	Instrument Preset. Sets counter to power-up default state
MD	CALC:STAT OFF	Disables Math function (default)
ME	CALC:STAT ON	Enables Math function
NA	SENS:AVER OFF	Disables 100 sample averaging mode
NW	CONF1:NWID	Selects Negative pulse width A measurement mode
PA	CONF1:PER	Selects Period A measurement mode
PH	CONF1:PHAS	Selects Phase A relative to B measurement mode
PW	CONF1:PWID	Selects Positive Pulse Width A measurement mode
Q0	*SRE 0	SRQ assertion unconditionally inhibited
Q1	ESE 60;SRE 4	SRQ assertion upon error detection
Q2	*SRE 16	SRQ asserted for measurement ready
Q3	ESE 60;SRE 20	SRQ asserted for measurement ready or error detection
Q4	Not implemented in 2461C	SRQ asserted for frequency standard change
Q5	Not implemented in 2461C	SRQ asserted for frequency standard change or error detection
Q6	Not implemented in 2461C	SRQ asserted for frequency standard change or measurement ready
Q7	Not implemented in 2461C	SRQ asserted for frequency standard change or error detection or measurement ready
R0	ARM:STAR:SOUR TTLT0	External arm input from TTLTRG0
R1	ARM:STAR:SOUR TTLT1	External arm input from TTLTRG1
R2	ARM:STAR:SOUR TTLT2	External arm input from TTLTRG2
R3	ARM:STAR:SOUR TTLT3	External arm input from TTLTRG3
R4	ARM:STAR:SOUR TTLT4	External arm input from TTLTRG4
R5	ARM:STAR:SOUR TTLT5	External arm input from TTLTRG5
R6	ARM:STAR:SOUR TTLT6	External arm input from TTLTRG6
R7	ARM:STAR:SOUR TTLT7	External arm input from TTLTRG7
R8	ARM:STAR:SOUR EXT	Enable external arm input on front panel
RA	CONF1:FREQ:RAT	Selects Ratio A/B measurement mode
RC	CONF3:FREQ:RAT	Selects Ratio C/B measurement mode
RDT	TINT:DEL:TIME?	Recalls arming delay time
RE	READ?	Resets measurement
RF	TOT:GAT:INT	Reads total so far
RGS	*IDN? (first rev. number listed)	Recalls VXIbus Processor firmware revision
RGT	SENS:APER?	Recalls Gate Time
RLA	INP1:COMP:LEV?	Recalls Input A trigger level
RLB	INP2:COMP:LEV?	Recalls Input B trigger level
RMn	Not implemented in 2461C	Recalls memory setting n. Sets counter to pre-stored configuration.
RMS	*IDN? (second rev. number listed)	Recalls counter firmware revision
RMX	CALC:MATH:EXPR?	Recalls math constant X
RMY	CALC:MATH:EXPR?	Recalls math constant Y
RMZ	CALC:MATH:EXPR?	Recalls math constant Z
RRS	SENS:RES?	Recalls measurement resolution
RSF	Not needed for 2461C	Recalls special function number
RT	CONF:RTIM	Selects Rise Time A measurement mode
RUT	Not implemented in 2461C	Recalls unit type
S10	ARM:SOUR INT;STOP:SOUR INT	Arming Mode: Start: Internal Stop: Internal
S11	ARM:SLOP POS;SOUR EXT;STOP:SOUR INT	Arming Mode: Start: External +ve Stop: Internal
S12	ARM:SLOP NEG;SOUR EXT;STOP:SOUR INT	Arming Mode: Start: External -ve Stop: Internal
S15	ARM:SLOP POS;SOUR EXT;STOP:SLOP POS;STOP:SOUR EXT	Arming Mode: Start: External +ve Stop: External +ve
S16	ARM:SLOP POS;SOUR EXT;STOP:SLOP NEG;STOP:SOUR INT	Arming Mode: Start: External +ve Stop: External -ve
S17	ARM:SLOP NEG;SOUR EXT;STOP:SLOP POS;STOP:SOUR EXT	Arming Mode: Start: External -ve Stop: External +ve
S18	ARM:SLOP NEG;SOUR EXT;STOP:SLOP NEG;STOP:SOUR INT	Arming Mode: Start: External -ve Stop: External -ve
S20	RES	Selects default configuration of Input A and B/Cancels S21
S21	All meas. Functions are interchangeable	Interchanges Inputs A and B
S30	INP:COMP:SET:AUTO:ON	Selects continuous auto-trigger measurement
S31	INP:COMP:SET:AUTO:ONCE	Selects single shot auto-trigger measurement
S50	CONF1:VOLT:MID	Selects Mean Amplitude measurement mode
S51	CONF1:VOLT:MAX	Selects Positive Peak amplitude measurement mode
S52	CONF1:VOLT:MIN	Selects Negative Peak amplitude measurement mode
S60	SENS1:TOT:GAT ON	Selects Totalize A by B measurement mode with TA command
S61	SENS1:TOT:GAT OFF	Selects Manual Totalize measurement mode with TA command
S70	CONF:CHECk	Enables check mode with CK command
S72	CONF:CHECk;TEST:STAT ON;:TEST: TEC:SHORT ON	Start TEC short continuous calibration in CK mode
S73	CONF:CHECk;TEST:STAT ON;:TEST: TEC:LONG ON	Start TEC long continuous calibration in CK mode
S74	CONF:CHECk;TEST:STAT ON;:TEST: TEC:SHORT ON	Start TEC short calibration in CK mode
S75	CONF:CHECk;TEST:STAT ON;:TEST: TEC:LONG ON	Start TEC long calibration in CK mode
S76	CONF:CHECk;TEST:STAT ON;:TEST:DAC ON	Check Input A and B DACs (continuously ramped) in CK mode
S77	CONF:CHECk;TEST:STAT ON;:TEST1:RELay ON	Input A relay check (requires 10MHz signal) in CK mode
S78	CONF:CHECk;TEST:STAT ON;:TEST2:RELay ON	Input B relay check (requires 10MHz signal) in CK mode
S80	Not implemented in 2461C	Enables 2 character function header on readback string
S81	Default state of the 2461C	Disables 2 character function header on readback string
SDTn	TINT:DEL:TIME n	Sets arming delay time to n seconds
SFD	Not required for 2461C	Disables special functions
SFE	Not required for 2461C	Enables special functions
SGTn	APER n	Sets gate time to n seconds
SLAv	INP1:COMP:LEV v	Sets Input A trigger level to v Volts
SLBv	INP2:COMP:LEV v	Sets Input B trigger level to v Volts
SMn	Not implemented in 2461C	Stores the present configuration in state n (0 to 9)
SMXa	CALC:MATH:EXPR a,b,c	Sets math constant X = a
SMYb	CALC:MATH:EXPR a,b,c	Sets math constant Y = b
SMZc	CALC:MATH:EXPR a,b,c	Sets math constant Z = c
SRSm	RES m	Sets measurement resolution in digits (3 to 10)
T0	INIT:CONT ON	Selects continuous measurement mode
T1	INIT:CONT OFF	Selects Single shot measurement mode
T2	TOT:GAT:MAN	Starts Manual Totalize or triggers a measurement cycle in T1 (single shot) mode
T3	TOT:GAT:MAN	Stops Manual Totalize
TA	CONF:TOT	Selects Totalize A by B measurement mode
TI	CONF:TINT	Selects Time Interval measurement mode
TRG	TRIG	Triggers the counter to take a measurement

Notes:
2251 Operation	2461C Equivalent	Comments
Read output buffer	READ?	2251 is constantly updating the input buffer; 2461C does when prompted to
Special functions	No action required	Nothing special needs to be done to access any 2461C functions