Atmel C51 - Manual (Page 10)

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.