Table 1. scales for monitor channels, Table 2. signal comparison, Monitor/v – Rainbow Electronics DS1858 User Manual
Page 9
DS1858
Dual Temperature-Controlled Resistors with
Three Monitors
_____________________________________________________________________
9
Monitored Signals
Each signal (V
CC
, MON1, MON2, MON3, and tempera-
ture) is available as a 16-bit value with 12-bit accuracy
(left-justified) over the serial bus. See
Table
1 for signal
scales and
Table
2 for signal format. The four LSBs
should be masked when calculating the value.
The signals are updated every frame rate (t
frame
) in a
round-robin fashion.
The comparison of all five signals with the high and low
user-defined values are done automatically. The corre-
sponding flags are set to 1 within a specified time of
the occurrence of an out-of-limit condition.
Calculating Signal Values
The LSB = 100µV for V
CC
, and the LSB = 38.147µV for
the MON signals.
To calculate the value of V
CC
, convert the unsigned 16-
bit value to decimal and multiply by 100µV.
To calculate the value of MON1, MON2, or MON3 con-
vert the unsigned 16-bit value to decimal and multiply
by 38.147µV.
To calculate the value of the temperature, treat the
two’s complement value binary number as an unsigned
binary number, then convert to decimal and divide by
256. If the result is greater than or equal to 128, then
subtract 256 from the result.
Temperature: high byte: -128
°C to +127°C signed; low
byte: 1/256
°C.
SIGNAL
+FS
SIGNAL
+FS
(hex)
-FS
SIGNAL
-FS
(hex)
Temperature
127.996
°C
7FFF
-128
°C
8000
V
CC
6.55V
FFFF
0V
0000
MON1
2.5V
FFFF
0V
0000
MON2
2.5V
FFFF
0V
0000
MON3
2.5V
FFFF
0V
0000
Table 1. Scales for Monitor Channels
SIGNAL
FORMAT
V
CC
Unsigned
MON1
Unsigned
MON2
Unsigned
MON3
Unsigned
Temperature
Two’s complement
Table 2. Signal Comparison
TEMPERATURE
CORRESPONDING LOOK-UP
TABLE ADDRESS
<-40
°C
80h
-40
°C
80h
-38
°C
81h
-36
°C
82h
-34
°C
83h
—
—
+98
°C
C5h
+100
°C
C6h
+102
°C
C7h
>+102
°C
C7h
Table 3. Look-up Table Address for
Corresponding Temperature Values
MSB
2
15
2
14
2
13
2
12
2
11
2
10
2
9
2
8
LSB
2
7
2
6
2
5
2
4
2
3
2
2
2
1
2
0
MSB (BIN)
LSB (BIN)
VOLTAGE (V)
10000000
10000000
3.29
11000000
11111000
4.94
S
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
MSB (BIN)
LSB (BIN)
TEMPERATURE (
°C)
01000000
00000000
64
01000000
00001111
64.059
01011111
00000000
95
11110110
00000000
-10
11011000
00000000
-40
MSB (BIN)
LSB (BIN)
VOLTAGE (V)
11000000
00000000
1.875
10000000
10000000
1.255
Monitor/V
CC
Bit Weights
Temperature Bit Weights
Monitor Conversion Example
V
CC
Conversion Examples
Temperature Conversion Examples