Atmel AT89EVK-01, Руководство пользователя

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Hardware Description
AT89EVK-01 User Guide 2-7
4325C–SCR–09/04
the TWI_SEL switch selects the polarity of the smart card presence: information on
PRES or on PRES\ (see §2.1.8). See Figure 4-1 on page 16 for TWI_SEL selection.
Figure 2-4. Power Supply Configuration
Remark:
VCC and L1 must be connected to the same voltage.
2.1.6 TWI Link The TWI link is managed by T89C5121. The program stored in the Flash memory con-
figures the AT83C24 registers once after the reset.
The T89C5121 sends TWI commands. The AT83C24 TWI address depends on level on
A2,A1,A0 pins at reset. The T89C5121 sends TWI commands at all addresses to avoid
any problem of level on A2, A1, A0 at reset.
2.1.7 External TWI Link If the user wants to use an external TWI source to configure the AT83C24, the 2 test
points SCL and SDA are used.
To avoid any conflict with T89C5121 signals, the T89C5121 software must check the
SW2 signal before to send data on SCL and SDA.
2.1.8 Board configuration The table below describes the switches and solder pads configurations.
AT83C24
VCC
LI
L1
VDDP TDA8004 (5V)
EVCC
VDD TDA8004 (3.3V or 5V)
Table 2-2. Configuration Description
Solder pad
or Switch
Default
Configuration Description
SW1 no solder RFU (TDA8004AT)
SW2 TWI_SEL = 0 Smart card presence detection:
TWI_SEL = 0: PRES indicates the smart card presence.
TWI_SEL = 1: PRES\ indicates the smart card presence.
SW5 Reset button
SW4 with solder Used for clock configuration (see §2.1.2)
SW9 solder Used to connect TDA8004 clock on A2 (transparent
mode). Use firmware from version 3 (at89evk01_V3.zip)
SW11 no solder Used to connect a pull up resistor on RESET pin