Rainbow Electronics AT89C5122 - Manual (Page 89)

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AT8xC5122/23
4202E–SCR–06/06
mode by 20% by means of bit OVFADJ in DCCKPS register. When the current overflow
controller is operating, the ICARDOVF is set by the hardware in SCISR register.
The current drawn from power supply by the DC/DC converter is controlled during the
startup phase in order to avoid high transient current mainly in Pump Mode which could
cause the power supply voltage to drop dramatically. This control is done by means of
bits BOOST[1:0], which increases progressively the startup current level.
Initialization Procedure The initialization procedure is different depending upon the required Card Vcc. One pro-
cedure apply for Card Vcc =< 3 volts and one procedure for Card Vcc = 5 volts.
The initialization procedure involves :
• Select the CVCC level by means of bits VCARD[1:0] in SCICR register,
• Set bits BOOST[1:0] in DCCKPS register following the current level control wanted.
• Switch the DC/DC on by means of bit CARDVCC in SCCON register,
• Monitor bit VCARDOK in SCISR register in order to know when the DC/DC
Converter is ready (CVCC voltage has reached the expected level)
Procedure for CVcc =< 3 volts The DC/DC regulation mode must be selected for Card Vcc = 1.8 volts and Card Vcc =
3 volts (MODE = 1 in DCCKPS register) The detailed procedures is described in flow
chart of Figure 46. for Card Vcc = 1.8 volts and in the flow chart of Figure 47. for Card
Vcc = 3 volts