Atmel AT89EVK-01, User Manual

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Hardware Description
2-6 AT89EVK-01 User Guide
4325C–SCR–09/04
Two solutions are proposed for the clock generation: waveform generator or crystal.
Figure 2-2. External Waveform Generator for Clock
Figure 2-3. Crystal for Clock
A solder pad (SW4) is used to configure the source: crystal or external waveform
generator.
2.1.3 Smart Card Clock
Signal (CCLK) 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.
2.1.4 Power Supply 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.
2.1.5 PRES, PRES\ 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
Table 2-1. Clock Solder Pads Configuration
SW4 Configuration
without solder Waveform generator
with solder crystal
SO plug
AT83C24
AT89C5121
RESET
AT83C24 2.0.0
ATMEL
SCL
SDA
Rx
Tx
VCC
VSS
XTAL1
waveform
generator
SO plug
AT83C24
AT89C5121
RESET
AT83C24 2.0.0
ATMEL
SCL
SDA
Rx
Tx
VCC
VSS
XTAL1
14.74MHz