DS83C520 Maxim, DS83C520 Datasheet - Page 26

• Manufacturer Part Number: DS83C520
• Description: The DS87C520/DS83C520 EPROM/ROM high-speed microcontrollers are fast 8051-compatible microcontrollers
• Manufacturer: Maxim

Table 9. EPROM Programming Modes
Table 10. DS87C520 EPROM Lock Bits
SECURITY OPTIONS
The DS87C520 employs a standard three-level lock that restricts viewing of the EPROM contents. A 64-
byte Encryption Array allows the authorized user to verify memory by presenting the data in encrypted
form.
Lock Bits
The security lock consists of three lock bits. These bits select a total of four levels of security. Higher
levels provide increasing security but also limit application flexibility. Table 10 shows the security
settings. Note that the programmer cannot directly read the state of the security lock. User software has
access to this information as described in the Memory section.
Program Code Data
Verify Code Data
Program Encryption Array
Address 0-3Fh
Program Lock Bits
Program Option Register
Address FCh
Read Signature or Option
Registers 30, 31, 60 FCh
LEVEL
1
2
3
4
MODE
LB1
U
P
P
P
LB1
LB2
LB3
LOCK BITS
LB2
U
U
P
P
RST
H
H
H
H
H
H
H
H
PSEN
LB3
L
L
L
L
L
L
L
L
U
U
U
P
ALE/PROG
No program lock. Encrypted verify if encryption table was
programmed.
Prevent MOVC instructions in external memory from reading
program bytes in internal memory. EA is sampled and latched on
reset. Allow no further programming of EPROM.
Level 2 plus no verify operation. Also, prevent MOVX
instructions in external memory from reading SRAM (MOVX) in
internal memory.
Level 3 plus no external execution.
DS87C520/DS83C520 EPROM/ROM High-Speed Microcontrollers
PL
PL
PL
PL
PL
PL
H
H
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EA/VPP
12.75V
12.75V
12.75V
12.75V
12.75V
12.75V
H
H
PROTECTION
P2.6
H
H
L
H
L
L
L
L
P2.7
H
H
H
H
H
L
L
L
P3.3
H
H
H
H
H
H
L
L
P3.6
H
H
H
H
L
L
L
L
P3.7
H
H
H
H
L
L
L
L