73S1209F Data Sheet
DS_1209F_004
102
Rev.
1.2
1.7.14 VDD Fault Detect Function
The 73S1209F contains a circuit to detect a low-voltage condition on the supply voltage V
DD
. If enabled,
it will deactivate the active internal smart card interface when V
DD
falls below the V
DD
Fault threshold. The
register configures the V
DD
Fault threshold for the nominal default of 2.3V* or a user selectable threshold.
The user’s code may load a different value using the FOVRVDDF bit =1 after the power-up cycle has
completed
VDDFault Control Register (VDDFCtl): 0xFFD4
Å
0x00
Table 109: The VDDFCtl Register
MSB
LSB
– FOVRVDDF
VDDFLTEN
– STXDAT.3 VDDFTH.2 VDDFTH.1 VDDFTH.0
Bit Symbol
Function
VDDFCtl.7 –
VDDFCtl.6 FOVRVDDF
Setting this bit high will allow the VDDFLT(2:0) bits set in this register to
control the VDDFault threshold. When this bit is set low, the VDDFault
threshold will be set to the factory default setting of 2.3V*.
VDDFCtl.5 VDDFLTEN Set = 1 will disable VDD Fault operation.
VDDFCtl.4 –
VDDFCtl.3 –
VDDFCtl.2 VDDFTH.2
VDD Fault Threshold.
Bit value(2:0) VDDFault voltage
000
2.3 (nominal default)
001
2.4
010
2.5
011
2.6
100
2.7
101
2.8
110
2.9
111
3.0
VDDFCtl.1 VDDFTH.1
VDDFCtl.0 VDDFTH.0
* Note: The V
DD
Fault factory default can be set to any threshold as defined by bits VDDFTH(2:0). The
73S1209F has the capability to burn fuses at the factory to set the factory default to any of these
voltages. Contact Teridian for further details.