Atmel AT89EVK-01 User Manual page 4

Hardware Description
2.1.3 Smart Card Clock
Signal (CCLK)
2.1.4 Power Supply
2.1.5 PRES, PRES\
2-6
4325C–SCR–09/04
Two solutions are proposed for the clock generation: waveform generator or crystal.
Figure 2-2. External Waveform Generator for Clock
waveform
generator
Figure 2-3. Crystal for Clock
14.74MHz
A solder pad (SW4) is used to configure the source: crystal or external waveform
generator.
Table 2-1. Clock Solder Pads Configuration
SW4
without solder
with solder
The AT83C24 outputs the smart card clock signal (CCLK). Two modes are available to
generate this signal:
1. The source is CLK. The CKS prescaler is used to divide CLK signal or DCCLK
signal.
2. The source is A2. The CKS prescaler is used to divide A2 signal.
The power supply comes from the TDA8004 footprint. The signal VDDP of the TDA8004
is used (5V).
The EVCC pin of the AT83C24 is connected to the VDD (3.3V). EVCC is used to supply
the AT83C24 pads connected to the customer application.
The TWI_SEL switch is connected on an I/O of the T89C5121. The TDA8004
(TDA8024) PRES pin and PRES\ pin are connected on T89C5121 I/Os. The position of
VSS
AT83C24
ATMEL
AT83C24 2.0.0
SO plug
AT89C5121
VCC
XTAL1
VSS
AT83C24
ATMEL
AT83C24 2.0.0
AT89C5121
VCC
XTAL1
SCL
SDA
RESET
Rx
Tx
SCL
SDA
SO plug
RESET
Rx
Tx
Configuration
Waveform generator
crystal
AT89EVK-01 User Guide