HP 6621A, 6623A, 6624A manual Unr +Cc, Asts?

Figure 5-3. Functional Relationship of Status Registers

The supply has one serial poll register which services all outputs and provides the user with other power supply status- related information as discussed on page 75.

Status Register. Each output channel of the power supply maintains its present status in an 8-bit register. This status register reports the status of the output channel whenever it is queried. A "1" in any of the bit positions indicates that the condition is true. As long as the condition continues to be true, the bit will remain set. Assignments for the bits are shown in Table 5-5.

Decoding of the reading is based on the weighted number placed on each bit of the 8-bit status registers. For example, bit position 5 in the register has a bit weight of 32 (see Table 5-5). Each bit is assigned to a particular condition and the corresponding bit weight is used to identify that condition. When set, bit 5 indicates that the associated output is in the unregulated state. If this is the only bit that is set, the number 32 will be returned when the output's status register is queried.

Table 5-5. Bit Alignment for the Status, A Status, Fault, and Mask Register

Bit Position	7	6	5	4	3	2	1	0
Bit Weight	128	64	32	16	8	4	2	1
Meaning	CP	OC	UNR	OT	OV	-CC	+CC	CV
Where

CV = Constant Voltage Mode

+CC = Positive Constant Current Mode - CC = Negative Current Limit Mode

OV = Overvoltage Protection circuit tripped

OT = Over Temperature Protection circuit tripped UNR = Unregulated Mode

OC = Over Current Protection tripped CP = Coupled parameter (See Note)

Note: When the range is automatically switched as discussed on page70, the CP bit is set. It is cleared when you send a voltage or current value that causes no range change.

To query an output channel for its status, you must specify the output channel. For example, to find out the status at output

2 send the following query and address the supply to talk:

STS? 2

Accumulated Status Register. Each output channel of the power supply also maintains a cumulative status in its accumulated status (astatus) register. This register records every status condition the power supply output entered since it was last queried. When queried, it returns a decimal number which is decoded as shown below. The astatus register is reset to the present value of the status register after it is queried. The bits are assigned as in Table 5-5. Here is an example to help you decode the decimal number (from 0 to 255) returned when the astatus register is queried. If the output channel was in overvoltage since the last reading of the astatus register and that channel is presently operating in constant voltage mode, the reading you will get when you query the register will be 9. To decode this we use table 5-5.

9 =	8	+	1
	OV	+	CV

For example, to query the astatus register of output 2, send the following query and address the supply to talk.

ASTS? 2

74 Remote Operation