Rainbow Electronics LM77 - Manual (Page 11)

1.0 Functional Description
(Continued)
1.9 POINTER REGISTER
(Selects which registers will be read from or written to):
P7 P6 P5 P4 P3 P2 P1 P0
0 0 0 0 0 Register Select
P0–P2: Register Select:
P2 P1 P0 Register
0 0 0 Temperature (Read only) (Power-up
default)
0 0 1 Configuration (Read/Write)
0 1 0 T
HYST
(Read/Write)
0 1 1 T_CRIT (Read/Write)
1 0 0 T
LOW
(Read/Write)
1 0 1 T
HIGH
(Read/Write)
P3–P7: Must be kept zero.
1.10 TEMPERATURE REGISTER
(Read Only):
D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0
Sign Sign Sign Sign MSB Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
CRIT HIGH LOW
Status Bits
D0–D2: Status Bits
D3–D15: Temperature Data. One LSB = 0.5˚C. Two’s complement format.
1.11 CONFIGURATION REGISTER
(Read/Write):
D7 D6 D5 D4 D3 D2 D1 D0
0 0 0 Fault Queue INT Polarity T_CRIT_A
Polarity
INT Mode Shutdown
D0: Shutdown - When set to 1 the LM77 goes to low power shutdown mode. Power up default of “0”.
D1: Interrupt mode - 0 is Comparator Interrupt mode, 1 is Event Interrupt mode. Power up default of “0”.
D2, D3: T_CRIT_A and INT Polarity - 0 is active low, 1 is active high. Outputs are open-drain. Power up default of “0”
D4: Fault Queue - When set to 1 the Fault Queu is enabled,
see
Section 1.7. Power up default of “0”.
D5–D7: These bits are used for production testing and must be kept zero for normal operation.
1.12 T
HYST
, T
LOW
, T
HIGH
AND T_CRIT_A REGISTERS
(Read/Write):
D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0
Sign Sign Sign Sign MSB Bit7 Bit6 Bit5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 X X X
D0–D2: Undefined
D3–D15: T
HYST
, T
LOW
, T
HIGH
or T_CRIT Trip Temperature Data. Power up default is T
LOW
= 10˚C, T
HIGH
= 64˚C, T_CRIT = 80˚C,
T
HYST
= 2˚C.
T
HYST
is subtracted from T
HIGH
, and T_CRIT, and added to T
LOW
.
Avoid programming setpoints so close that their hysteresis values overlap. See Section 1.1.
LM77
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