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Atmel C51 Manuale Utente

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Hardware Description
2-7
C51 Microcontrollers Demo Board User Guide
4119C–8051–3/03
Figure 2-5.  C51/C251 Demo Board
2.6
J11 Switches
Table 1.  J11 Switches
(Set=1, Clear=0)
J11
J9
J16
RS232 Cable to Terminal
J8
J8
LCD CTRST
+
RESET
INT1
OFF
ON
J17
R21
Page Mode
Non Page Mode
Synchro IN
Synchro OUT
RS232
LCD
1
1
1
X2
X3
X1
PLCC44
PLCC68
DIL24
Extension connector
7
6
5
4
3
2
1
0
ISP
ALE
PSEN
UC4
UC3
UC2
UC1
UC0
Bit 
Number
Bit 
Mnemonic
Description
7
ISP1
In-System Programming (external Flash memory)
Set to enable external Flash memory programming 
Clear to protect external Flash memory from erasure and programming
6
ALE
Address Latch Enable
Set to see ALE activity
Clear to ground ALE
5
PSEN
Program Store Enable
Set to run demos
Clear to program T89C51RD2 on-chip Flash memory
4-0
UC4:0
User Code
Free of use as data input for demos.