Datasheet
TC74
DS21462D-page 8 2001-2012 Microchip Technology Inc.
4.0 REGISTER SET AND
PROGRAMMER’S MODEL
TABLE 4-1: COMMAND BYTE
DESCRIPTION
(SMBUS/I
2
C READ_BYTE AND
WRITE_BYTE)
TABLE 4-2: CONFIGURATION REGISTER
(CONFIG); 8 BITS, READ/
WRITE)
FIGURE 4-1: DATA_RDY, SHDN
Operation Logic Diagram.
4.1 Temperature Register (TEMP),
8 Bits, READ ONLY
The binary value (2’s complement format) in this regis-
ter represents temperature of the onboard sensor
following a conversion cycle. The registers are
automatically updated in an alternating manner.
TABLE 4-3: TEMPERATURE REGISTER
(TEMP)
I
n temperature data registers, each unit value repre-
sents one degree (Celsius). The value is in 2’s
complement binary format such that a reading of 0000
0000b corresponds to 0°C. Examples of this
temperature to binary value relationship are shown in
Table 4-4
.
TABLE 4-4: TEMPERATURE-TO-DIGITAL
VALUE CONVERSION
(TEMP)
4.2 Register Set Summary
The TC74 register set is summarized in Table 4-5. All
registers are 8 bits wide.
TABLE 4-5: TC74 REGISTER SET
SUMMARY
Command Code Function
RTR 00h Read Temperature (TEMP)
RWCR 01h Read/Write Configuration
(CONFIG)
Bit POR Function Type Operation
D[7] 0 STANDBY
Switch
Read/
Write
1 = standby,
0 = normal
D[6] 0 Data Ready * Read
Only
1 = ready
0 = not ready
D[5]-
D[0]
0 Reserved -
Always
returns zero
when read
N/A N/A
Note 1: *DATA_RDY bit RESET at power-up and
SHDN enable.
V
DD
DATA_RDY
SHDN
t
conv
t
conv
D[7] D[6] D[5] D[4] D[3] D[2] D[1] D[0]
MSB X X X X X X LSB
Actual
Temperature
Registered
Temperature
Binary
Hex
+130.00°C +127°C 0111 1111
+127.00°C +127°C 0111 1111
+126.50°C +126°C 0111 1110
+25.25°C +25°C 0001 1001
+0.50°C 0°C 0000 0000
+0.25°C 0°C 0000 0000
0.00°C 0°C 0000 0000
-0.25°C -1°C 1111 1111
-0.50°C -1°C 1111 1111
-0.75°C -1°C 1111 1111
-1.00°C -1°C 1111 1111
-25.00°C -25°C 1110 0111
-25.25°C -26°C 1110 0110
-54.75°C -55°C 1100 1001
-55.00°C -55°C 1100 1001
-65.00°C -65°C 1011 1111
Name Description
POR
State
Read Write
TEMP Internal Sensor
Temperature (2’s
Complement)
0000
0000b
(1)
N/A
CONFIG CONFIG
Register
0000
0000b
Note 1: The TEMP register will be immediately
updated by the A/D converter after the
DATA_RDY Bit goes high.