Part 7.3: Real Time Clock Ds1302 - Alinx ZYNQ 7000 User Manual

ZYNQ FPGA Development Board AX7020 User Manual

Part 7.3: Real Time Clock DS1302

The development board contains a real-time clock RTC chip, model
DS1302, which provides a calendar function up to 2099, with days, minutes,
minutes, seconds and weeks. If time is needed in the system, then the RTC
needs to be involved in the product. It needs to connect a 32.768KHz passive
clock to provide an accurate clock source to the clock chip, so that the RTC can
accurately provide clock information to the product. At the same time, in order
to power off the product, the real-time clock can still operate normally.
Generally, a battery is required to supply power to the clock chip. In Figure 7-8,
the BT1 is the battery holder, and the button battery (model CR1220, voltage is
3V) is placed. After the system is turned off, the button battery can also supply
power to the DS1302. This way, regardless of whether the product is powered
or not, the DS1302 will operate normally without interruption and provide
continuous time information. The RTC interface signal is connected to the IO
ports of BANK34 and BANK35 on the ZYNQ PL side. Figure 7-7 shows the
design of the DS1302:
Figure 7-7: Real time clock DS1302 Schematic
38 / 47