Rainbow Electronics LM81 - Manual (Page 23)

Functional Description
(Continued)
masks for each Interrupt. As described in Section 3.3, the
hardware Interrupt line can also be enabled/disabled in the
Configuration Register.
T_CRIT_A interrupt is dedicated to temperature and is indi-
cated in Extended Mode Register 1. Extended Mode Regis-
ter 1 controls T_CRIT_A.
9.1 Interrupt Clearing
Reading a Status Register will output the contents of the
Register, and reset the Register. A subsequent read done
before the analog “round-robin” monitoring loop is complete
will indicate a cleared Register. Allow at least 820 ms to allow
all Registers to be updated between reads. In summary, the
Interrupt Status Register clears upon being read, and re-
quires at least 400 ms to be updated. When the Interrupt
Status Register clears, the hardware interrupt line will also
clear until the Registers are updated by the monitoring loop.
The hardware Interrupt line (INT) is cleared with the
INT_Clear bit, which is Bit 3 of the Configuration Register.
When this bit is high, the LM81 monitoring loop will stop. It
will resume when the bit is low.
10.0 RESET I/O
RESET is intended to provide a master reset to devices
connected to this line. INT Mask Register 2, Bit 7, must be
set high to enable this function. Setting Bit 4 in the Configu-
ration Register high outputs a least 20 ms low on this line, at
the end of which Bit 4 in the Configuration Register automati-
cally clears. Again, the label for this pin is only its suggested
use. In applications where the RESET capability is not
needed it can be used for any type of digital control that
requires a 20 ms active low open-drain output.
RESET operates as an input when not activated by the
Configuration Register. Setting this line low will reset all of
the registers in the LM81 to their power on default state. All
Value RAM locations will not be affected except for the DAC
Data Register.
11.0 NAND TREE TESTS
A NAND tree is provided in the LM81 for Automated Test
Equipment (ATE) board level connectivity testing. DACOut/
NTEST_IN, T_CRIT_A, V
+ and GND pins are excluded from
NAND tree testing. Taking DACOut/NTEST_IN high before
the first write to the configuration register activates the
NAND Tree test mode. After the first write to the configura-
tion register the NAND Tree test mode cannot be reacti-
vated. To perform a NAND tree test all pins included in the
NAND tree should be driven to 1 forcing the A0/
NTEST_OUT high. Each individual pin starting with A1 and
concluding with SMBData (excluding DACOut/NTEST_IN,
T_CRIT_A, V
+ and GND) can be taken low with the resulting
toggle observed on the A0/NTEST_OUT pin. Allow for a
typical propagation delay of 500 ns.
DS100072-29
LM81
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