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Programming and reading registers
Programming enable registers
The only registers that can be programmed by the user are the enable registers. All other reg-
isters 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 com-
mands are covered later in this section (Tables 14-3 and 14-6).
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 14-2) indicate the binary parameter value. For exam-
ple, 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, convert the
binary number to its decimal, hexadecimal, or octal equivalent:
Binary 11010 = Decimal 26 = Hexadecimal 1A = Octal 32
Note that Figure 14-2 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 14-2
16-bit status
register
A) Bits 0 through 7
Bit Position
B7
Binary Value
0/1
Decimal
128
( 2
7
)
Weights
B) Bits 8 through 15
Bit Position
B15
0/1
Binary Value
Decimal
32768 16384 8192
Weights
( 2
15
)
B6
B5
B4
B3
0/1
0/1
0/1
0/1
64
8
32
16
( 2
6
)
( 2
5
)
( 2
4
)
( 2
3
)
B14
B13
B12
B11
0/1
0/1
0/1
0/1
4096 2048 1024
( 2
14
)
( 2
13
)
( 2
12
)
( 2
11
)
Status Structure
B2
B1
B0
0/1
0/1
0/1
4
1
2
( 2
2
)
( 2
1
)
( 2
0
)
B10
B9
B8
0/1
0/1
0/1
512
256
( 2
10
)
( 2
9
)
( 2
8
)
14-5
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