Linear Technology LTC2983 - Page 64

LTC2983
64
2983fc
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convention shown in Table 75, where the first 14 bits
are the integer part and the remaining 10 bits are the
fractional part.
In this example, a custom RTD tied to CH12/13, with a
sense resistor on CH10/11, is programmed with the chan-
nel assignment data shown in Table 76 (refer to Figure 15
for a similar format). In this case, the custom data begins
at memory location 0x28C (starting address is 10). The
starting address (offset from 0x250) is entered in the
custom RTD data pointer field of the channel assignment
data. The table data length –1 (9 in this case) is entered
into the custom RTD data length field of the channel as-
signment word. Refer to Table 72 where the total number
of paired entries is 10.
Table 75. Example RTD Temperature Values
BYTE 1 BYTE 2 BYTE 3
B23 B22 B21 B20 B19 B18 B17 B16 B15 B14 B13 B12 B11 B10 B9 B8 B7 B6 B5 B4 B3 B2 B1 B0
Temperature 2
13
2
12
2
11
2
10
2
9
2
8
2
7
2
6
2
5
2
4
2
3
2
2
2
1
2
0
2
–1
2
–2
2
–3
2
–4
2
–5
2
–6
2
–7
2
–8
2
–9
2
–10
112.3 0 0 0 0 0 0 0 1 1 1 0 0 0 0 0 1 0 0 1 1 0 0 1 1
200.56 0 0 0 0 0 0 1 1 0 0 1 0 0 0 1 0 0 0 1 1 1
1 0 1
273.16 0 0 0 0 0 0 1 0 0 1 0 0 0 1 0 0 1 0 1 0 0 0 1 1
377.25 0 0 0 0 0 0 1 1 1 1 1 0 0 1 0 1 0 0 0 0 0 0 0 0
489.66 0 0 0 0 0 0 0 1 1 0 1 0 0 1 1 0 1 0 1 0 0 0 1 1
595.22 0 0 0 0 1 0 0 1 0 1 0 0 1 1 0 0 1 1 1 0 0 0 0 1
697.87 0 0 0 0 1 0 1 0 1 1 1 0 0 1 1 1 0 1 1 1 1 0 1 0
765.14 0 0 0 0 1
1 0 1 1 1 1 1 0 1 0 0 1 0 0 0 1 1 1 1
801.22 0 0 0 0 1 0 1 0 1 0 0 0 0 1 0 0 1 1 1 0 0 0 0 1
900.5 0 0 0 0 1 1 1 0 0 0 0 1 0 0 1 0 0 0 0 0 0 0 0 0
Table 76. Custom RTD Channel Assignment Data
CONFIGURATION
FIELD
DESCRIPTION # BITS BINARY
DATA
MEMORY
ADDRESS 230
MEMORY
ADDRESS 231
MEMORY
ADDRESS 232
MEMORY
ADDRESS 233
(1) RTD Type Custom 5 10010 1 0 0 1 0
(2) Sense Resistor
Channel Pointer
CH
11
5 01011 0 1 0 1 1
(3) Sensor
Configuration
4-Wire, No
Rotate, No Share
4 1000 1 0 0 0
(4) Excitation Current 25µA 4 0011 0 0 1 1
(5) Curve Not Used for
Custom
2 00 0 0
(6) Custom RTD Data
Pointer
Start Address
= 10
6 001010 0 0 1 0 1 0
(6) Custom RTD Data
Length-1
Data Length –1
= 9
10 Paired Entries
6 001001 0 0 1 0 0 1
CUSTOM RTDS