Part 3.8 : Real Time Clock Ds1302 - Alinx AX7050 User Manual

Part 3.8 : Real time clock DS1302

The AX7050 FPGA Carrier 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
3-8-2, 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 interface signal of the RTC is also
connected to the BANK16 IO port of the FPGA. Figure 3-8-1 shows the design
of the DS1302:
FPGA
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Spartan-7 FPGA Development Board AX7050 User Manual
I2C_SCL
I2C_SDA
U6
Y19
M17
M18
Figure 3-8-1: Real time clock DS1302 Schematic
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3.3V
RTC_SCLK
SCLK
RTC_DATA
I/O
RTC_RESET
/RST
A19
A18
3.3V
U4
VCC2
VCC1
DS1302
X1
X2