Évaluations - 5, GPA: 4
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Facilité d'utilisation
The controller cannot send commands to a second instrument until the handshake is Operating Instructions 59 completed with the first. Therefore, sending device trigger after sending a command assures that the second instrument cannot begin to receive commands until the first instrument has processed its commands. For example, assume the following commands are sent to four power supplies assigned to addresses called PS1, PS2, PS3, and PS4: OUTPUT PS1; "HOLD ON’’5A’ ’’ OUTPUT PS2; "HOLD ON; lA" TRIGGER PS1 TRIGGER PS2 OUTPUT PS3; "HOLD OFF; 10A" TRIGGER PS3 OUTPUT PS4; "HOLD OFF. 2A" Power supply 2 will start to change only after power supply 1 has started to change, and power supply 4 will start to change only after power supply 3 has started to change. Note that this feature concerns only the processing of the GP-IB command. The time required for the power supplies to settle at their new values depends on the load and on the direction and amount of change. Store/Recall. The power supply can store up to 16 complete power supply states except for output on/off. This allows the operator to preset frequently used values, which can then be recalled when needed with a single command. Preset values are stored and recalled using these codes (3 and 1 used as examples): STO 3 RCL 11 Sending a store command causes a "snapshot" of the present machine state to be stored. The power supply can then be programmed with new values. Note that only those values to be changed need be reprogrammed. For example, if the following command strings were sent in listed order to the power supply, the string stored in register 1 would include a current setting of 2 A and CC foldback in addition to a voltage setting of 6 V. The string stored in register 2 would include a voltage setting of 8 V in addition to a current setting of 5 A and CV foldback. Note that the stored because the output was turned off. The store/recall designators need not be assigned in consecutive order, but they must be in the range of 0 to 15. OUT OFF VSET 5V; ISET 2A; FOLD CC; STO 0 VSET 8V; STO 1 ISET 5A; FOLD CV; STO 2 Status Register. The power supply maintains an 9-bit status register that reflects the present state of the unit. Each of the nine bits represents a separate condition; when the condition is true the corresponding bit is 1. Bits are assigned as shown in Table 3-9. The status register can be read by sending: STS? and addressing the power supply to talk. The response from the power supply is in this format: STS xxx where xxx is a string of ASCII decimal digits. These digits specify an integer which is equal to the sum of the bit weights of the true conditions. 60 Operating Instructions For example, if bits for both ERR (128) and CC (2) are set, the power supply would send ASCII digits 1 3 0 (128 +2 = 130). Bits remain set in the status register as long as the corresponding conditions are true. Table 3-9. Status Register Bit Position 8 7 6 5 4 3 2 1 0 Bit Weight 256 128 64 32 16 8 4 2 1 Condition RI ERR FOLD AC OT OV OR CC CV CV Constant Voltage Mode CC Constant Current Mode OR Overrange OV Overvoltage Protection Circuit Tripped OT Overtemperature Protection Circuit Tripped AC AC Line Dropout or Out of Range FOLD Foldback Protection Circuit Tripped ERR Remote Programming Error RI Remote Inhibit (INH) Accumulated Status Register. Reading the status register provides the controller only the state of the power supply at the time STS? was received. A condition that lasts only momentarily may not be observed even with frequent polling of the status register. To ensure that a temporary change can be noted by the controller, the power supply maintains an accumulated status (astatus) register. Table 3-9 describes the astatus register as well as the status register. A bit in the astatus register will be 1 if the corresponding bit in the status register has been 1 at any time since the astatus register was last read. The astatus register can be read by sending: ASTS? and addressing the power supply to talk. The response from the power supply is in this format: ASTS xxx where xxx is decoded the same way as in the status register readback. The astatus register is reset to the present value of the status register immediately after it is read by the ASTS? query. Mask and Fault Registers. The power supply has two additional registers, the mask register and the fault register, both of which are arranged like the status register (Table 3-9). The mask register is maintained by the user, and is used to specify which bits in the status register are enabled (unmasked) to set bits in the fault register. A bit is set in the fault register when the corresponding bit in the status register changes from 0 to 1 and the corresponding bit in the mask register is 1. Whenever any bit is set in the fault register the FAU bit is set in the serial poll register. Operating Instructions 61 Note that bits can be set in the fault register only when there is a change in either the status ...
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