
 2002 Microchip Technology Inc.
DS20092A-page 11
TC77
4.0
INTERNAL REGISTER 
STRUCTURE
The TC77 Internal register structure consists of three
registers. The Temperature and Manufacturer’s Identi-
fication registers are read only, while the Configuration
register is write only.
TABLE 4-1:
REGISTERS FOR TC77
4.1
Configuration Register (CONFIG)
The Configuration register is write only. This register
selects either Shutdown, Continuous Conversion or
Test modes:
 C15:C0 = 
XXXX/XXXX 1111/1111
 (Shutdown 
mode)
 C15:C0 = 
XXXX/XXXX 0000/0000
 (Continuous 
Conversion mode)
 The TC77 is in Shutdown mode when bits C0 to 
C7 are all equal to ‘
1
’s. The TC77 will be in the 
Continuous Conversion mode if a ‘
0
’ in any bit 
location from C0 to C7 is written to the Configura-
tion register. The TC77 is in the Continuous 
Conversion mode at power-up.
It is recommended that the user write all ‘
0
’s or all ‘
1
’s
to the Configuration register because other bit codes
may put the TC77 in a test mode used for calibration
and production verification tests. Section 3.3 lists the
Configuration register bit codes that can be written to
the TC77 without having the device enter a production
test mode.
During Shutdown mode, the serial bus is still active.
The current consumption of the TC77 will be less than
1 μA during the time between serial communication.
4.2
Temperature Register (TEMP)
The Temperature register is read only and holds the
temperature conversion data. Bits 0 and 1 are unde-
fined and will be tri-state outputs during a read
sequence. Bit 2 is set to a logic ‘
1
’ after completion of
the first temperature conversion following a power-up
or reset event. Bit 2 is set to a logic ‘
0
’ during the time
needed to complete the first temperature conversion.
Therefore, the status of bit 2 can be monitored to indi-
cate that the TC77 has completed the first temperature
conversion. Bits 15:3 contain the 13 bit two’s comple-
ment data from the temperature conversion.
4.3
Manufacturer’s ID Register (M_ID)
The Manufacturer’s Identification code is contained in
this read only register. The Manufacturer ID register is
only available for a read operation when the TC77 is in
Shutdown mode. The Manufacturer’s ID code is con-
tained in bits 15:8 and is equal to 54 hex to indicate a
Microchip device. Bits 1:0 are undefined and will be tri-
state outputs during a read sequence, while bits 7:2 are
set to ‘
0
’.
Name
Bit 
15
Bit 
14
Bit 
13
Bit 
12
Bit 
11
Bit 
10
Bit 
9
Bit 
8
Bit 
7
Bit 
6
Bit 
5
Bit 
4
Bit 
3
Bit 
2
Bit 
1
Bit 
0
Value at Powerup/Reset
CONFIG
C15
C14
C13
C12
C11
C10
C9
C8
C7
C6
C5
C4
C3
C2
C1
C0
XXXX/XXXX 0000/0000
TEMP
T12
T11
T10
T9
T8
T7
T6
T5
T4
T3
T2
T1
T0
*
x
x
1111/1111 0000/0*XX
M_ID
* 
Bit 2 = 0 during power-up; otherwise, bit 2 =1
0
1
0
1
0
1
0
0
0
0
0
0
0
0
x
x
0101/0100 0000/00XX