Datasheet

Page 9
C2
100nF
VCC
C10
100nF
VCC
C13
100nF
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
U2
DIP40B
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20 21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
U1
DIP40A
VCC
PA0
PA1
PA2
PA3
PA4
PA5
PA6
PA7
PE0
OSC
PC0
PC1
PC2
PC3
PD0
PD1
PD7
PD6
PD5
PD4
PD3
PD2
PB4
PB3
PB2
PB1
PB0
PC7
PC6
PC5
PC4
PE1
PE2
PB5-MOSI
PB7-SCK
PB6-MISO
mRST#
OSC
PD0
PD1
PD7PD6
PD5
PD4
PD3
PD2
PB4
PB3
PB2
PB1
PB0 PA0
PA1
PA2
PA3
PA4
PA5
PA6
PA7
PC0
PC1
PC2
PC3
PC7
PC6
PC5
PC4
AREF
PB5-MOSI
PB7-SCK
PB6-MISO
mRST#
VCC
AVCC
C11
100nF
VCC
AVCC
FP2
FERRITE
1110
U3E
74HC04
5
6
U3C
74HC04
R13
1K
C3
22pF
C4
22pF
R12
1M
X1 8 MHz
OSC
1
2
U3A
74HC04
34
U3B
74HC04
9
8
U3D
74HC04
1312
U3F
74HC04
C1
100nF
VCC
DATA BUS
6. External Oscillator
Board contains 8MHz external crystal oscillator
which delivers the clock necessary for the
operation of microcontroller. Raw clock signal from
the crystal is sinusoidal, so additional 74HC04 is
provided which lters it to create square signal
necessary for stable operation.
Figure 6-2:
External clock module
Figure 6-1:
External Oscillator schematics