Keithley 6487 Reference Manual

Model 6487 Reference Manual Status Structure 10-5
Programming and reading registers
Programming enable registers
The only registers that can be programmed by the user are the enable registers. All other
registers in the status structure are read-only registers. The following explains how to
ascertain the parameter values for the various commands used to program enable registers.
The actual commands are covered later in this section (Table 10-3 through Table 10-6).
A command to program an event enable register is sent with a parameter value that deter-
mines the desired state (0 or 1) of each bit in the appropriate register. An enable register
can be programmed using any of the following data formats for the parameter value:
binary, decimal, hexadecimal, or octal.
The bit positions of the register (Figure 10-1) indicate the binary parameter value. For
example, if you wish to sets bits B4, B3, and B1, the binary value would be 11010 (where
B4=1, B3=1, B1=1 and all other bits are 0). When you use one of the other formats, con-
vert the binary number to its decimal, hexadecimal, or octal equivalent:
Binary 11010 = Decimal 26 = Hexadecimal 1A = Octal 32
Note that Figure 10-2 includes the decimal weight for each register bit. To set bits B4, B3,
and B1, the decimal parameter value would be the sum of the decimal weights for those
bits (16+8+2 = 26).
Figure 10-2
16-bit status register
The <NDN> (non-decimal numeric) parameter type is used to send non-decimal values.
These values require a header (#B, #H, or #Q) to identify the data format being sent. The
letter in the header can be upper or lower case. The <NRf> (numeric representation for-
B7
B15
B6 B5
B4
B3
B2 B1
B0
0/1
0/1
0/1
0/1
0/1
0/1
0/1
0/1
0/1
0/1
0/1
0/1
0/1
0/1
0/1
0/1
128
(2 )
7
32768
(2 )
15
64
(2 )
6
16384
(2 )
14
32
(2 )
5
8192
(2 )
13
16
(2 )
4
4096
(2 )
12
8
(2 )
3
2048
(2 )
11
4
(2 )
2
1024
(2 )
10
2
(2 )
1
512
(2 )
9
1
(2 )
0
256
(2 )
8
Bit Position
Bit Position
Binary Value
Binary Value
Decimal Weights
Decimal Weights
A. Bits 0 through 7
B. Bits 8 through 15
B14 B13 B12 B11 B10 B9 B8

Keithley 6487 Specifications

General

Type	Picoammeter/Voltage Source
Current Measurement Range	20 fA to 20 mA
Interfaces	GPIB, RS-232
Voltage Burden	< 200 µV
Input Impedance	>10^14 Ω
Power	100 V / 120 V / 220 V / 240 V
Basic Current Measurement Accuracy	0.4%