Maxim Integrated DS4830A Optical Microcontroller - Manual (Page 147)

DS4830A User’s Guide
147
SECTION 17 – SUPPLY VOLTAGE MONITOR (SVM)
The DS4830A provides feature to allow monitoring its power supply. The Supply Voltage Monitor (SVM) monitors the
V
DD
power supply and can alert the processor through an interrupt if V
DD
falls below a programmable threshold.
The DS4830A provides the following power monitoring features:
• SVM compares V
DD
against a programmable threshold from approximately 2.3V to 3.5V.
• Optional SVM interrupt can be triggered when V
DD
drops below the programmed threshold.
The Supply Voltage Monitor is controlled by the peripheral register SVM. This register is located in Module 1, Index
9.
Supply Voltage Monitor Register (SVM)
Bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Name - - - - SVTH[3:0] - - - - SVMI SVMIE SVMRDY SVMEN
Reset 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Access r r r r rw* rw* rw* rw* r r r rw rw rw r rw
*SVTH[3:0] bits can only be written when the SVM is not running (SVMEN=0)
BIT NAME DESCRIPTION
15:12 Reserved Reserved. The user should write 0 to these bits.
11:8 SVTH[3:0] Supply Voltage Threshold Bits [3:0]: These bits are used to select a user defined supply voltage
threshold. If V
DD
is below this threshold, the SVMI bit will be set and an interrupt can be generated if
enabled. The threshold level can be adjusted from 2.3V to 3.5V in 0.1V increments. The default
value is 00h (2.3V).
Supply Voltage Monitor Threshold = 2.3V + SVTH[3:0] * 0.1V
Note that the SVTH[3:0] bits can only be modified when SVMEN = 0. Writing to these bits is ignored
if SVMEN = 1. The SVM thresholds 00h to 05h have no actual µs because these are lower than the
DS4830A operating V
DDMIN
range (which is 2.85V). In the upper side, setting 0Ch to 0Fh corresponds
to 3.5V V
DD
.
7:4 Reserved Reserved. The user should write 0 to these bits.
3 SVMI Supply Voltage Monitor Interrupt: This bit is set to '1' when the V
DD
supply voltage falls below the
threshold defined by SVTH[3:0]. If SVMIE = 1, setting this bit to 1 by either hardware or software
triggers an interrupt. This bit must be cleared by software, but if V
DD
is still below the threshold, the bit
is immediately set again by hardware.
2 SVMIE Supply Voltage Monitor Interrupt Enable: Setting this bit to 1 allows an interrupt to be generated (if
not otherwise masked) when SVMI is set to 1. Clearing this bit to 0 disables the SVM interrupt.
1 SVMRDY Supply Voltage Monitor Ready: This read-only status bit indicates whether the SVM is ready for
use.
0 = The SVM is disabled (SVMEN = 0), or the SVM is in the process of powering up.
1 = The SVM is enabled and ready for use.
0 SVMEN Supply Voltage Monitor Enable: Setting this bit to 1 enables the SVM and begins monitoring V
DD
against the programmed (SVTH[3:0]) threshold. After SVMEN is set, SVMRDY will be set in
approximately 20 us. Clearing this bit to 0 disables the SVM.