unicore UM980 - Page 14

9
No.
Pin
I/O
Description
34
VCC
I
Power supply
35
NC
—
No connection inside; leave floating
36
V_BCKP
I
When the main power supply VCC is cut off,
V_BCKP supplies power to RTC and relevant
register. Level requirement: 2.0 V ~ 3.6 V, and
the working current should be less than 60
μA at 25 °C. If you do not use the hot start
function, connect V_BCKP to VCC. Do NOT
connect it to ground or leave it floating.
37
GND
—
Ground
38
NC
—
No connection inside; leave floating
39
NC
—
No connection inside; leave floating
40
NC
—
No connection inside; leave floating
41
GND
—
Ground
42
TXD1
O
COM1 output, LVTTL level
43
RXD1
I
COM1 input, LVTTL level
44
SDA
I/O
I
2
C data
45
SCL
I/O
I
2
C clock
46
NC
—
No connection inside; leave floating
47
NC
—
No connection inside; leave floating
48
GND
—
Ground
49
RESET_N
I
System reset; active Low. The active time
should be no less than 5 ms.
50
NC
—
No connection inside; leave floating
51
EVENT
I
Event mark input, with adjustable frequency
and polarity