Lakeshore Learning Materials 642 User Manual
Page 59
Lake Shore Model 642 Electromagnet Power Supply User’s Manual
Computer Interface Operation
5-7
5.1.4.1.6 Reading
Registers
Any register in the status system may be read using the appropriate query command. Some registers clear when read,
others do not. Refer to Paragraph 5.1.4.1.7. The response to a query will be a decimal value that corresponds to the
binary-weighted sum of all bits in the register, Refer to Table 5-1. The actual query commands are described later in
this section.
Table 5-1. Binary Weighting of an 8-Bit Register
Position B7 B6 B5 B4 B3 B2 B1 B0
Decimal 128
64 32 16 8 4 2 1
Weighting 2
7
2
6
2
5
2
4
2
3
2
2
2
1
2
0
Example: If bits 0, 2, and 4 are set, a query of the register will return a decimal value of 21 (1+4+16).
5.1.4.1.7 Programming
Registers
The only registers that may be programmed by the user are the enable registers. All other registers in the status system
are read-only registers. To program an enable register send a decimal value which corresponds to the desired binary-
weighted sum of all bits in the register, Refer to Table 5-1. The actual commands are described later in this section.
5.1.4.1.8 Clearing
Registers
The methods to clear each register are detailed in Table 5-2.
Table 5-2. Register Clear Methods
Register Method
Example
Condition Registers
None – registers are not latched
—
Query the event register.
*ESR?
(clears Standard Event
Status register)
Send *CLS
*CLS
(clears all three registers)
Event Registers:
Standard Event Status Register
Operation Event Register
Error Status Event Register
Power on instrument
—
Write 0 to the enable register.
*ESE 0
(clears Standard Event
Status Enable register)
Enable Registers:
Standard Event Status Enable
Register
Operation Event Enable Register
Error Status Enable Register
Service Request Enable Register
Power on instrument
—
There are no commands that directly clear
the Status Byte as the bits are non-
latching. To clear individual summary
bits, clear the event register that
corresponds to the summary bit. Sending
*CLS will clear all event registers which
in turn clears the status byte.
If bit 5 (ESB) of the Status
Byte is set, send *ESR? to
read the Standard Event
Status Register and bit 5
will clear.
Status Byte
Power on instrument
—