Rainbow Electronics DS8314 - Manual (Page 15)

Smart Card Power Select
The DS8313/DS8314 support three smart card V CC
voltages: 1.8V, 3V, and 5V. The power select is con-
trolled by the 1_8V and 5V/3V signals as shown in
Table 3. The 1_8V signal has priority over 5V/3V. When
1_8V is asserted high, 1.8V is applied to V
CC
when the
smart card is active. When 1_8V is deasserted, 5V/3V
dictates V
CC power range. V CC is 5V if 5V/3V is assert-
ed to a logic-high state, and V CC is 3V if 5V/3V is pulled
to a logic-low state. Care must be exercised when
switching from one V
CC power selection to the other. If
both 1_8V and 5V/3V are high with CMDVCC high at
the same time, the DS8313/DS8314 enter stop mode.
To avoid accidental entry into stop mode, the state of
1_8V and 5V/3V must not be changed simultaneously.
A minimum delay of 100ns should be observed
between changing the states of 1_8V and 5V/3V. See
Figure 9 for the recommended sequence of changing
the V
CC range.
DS8313/DS8314
Smart Card Interface
______________________________________________________________________________________ 15
V CC SELECT STOP MODE 1.8V 1.8V 3V 3V 5V
1_8V
5V/3V
CMDVCC
Figure 9. Smart Card Power Select
Table 3. V CC Select and Operation Mode
1_8V 5V/3V CMDVCC V CC SELECT (V) CARD INTERFACE STATUS
0 0 0 3 Activated
0 0 1 3 Inactivated
0 1 0 5 Activated
0 1 1 5 Inactivated
1 0 0 1.8 Activated
1 0 1 1.8 Inactivated
1 1 0 1.8 Reserved (Activated)
1 1 1 1.8 Not Applicable—Stop Mode