N87C51RB24 Intel, N87C51RB24 Datasheet - Page 18

• Manufacturer Part Number: N87C51RB24
• Description: IC MCU 8BIT 16K 24MHZ OTP 44PLCC
• Manufacturer: Intel
• Series: 87Cr

Specifications of N87C51RB24

• Rohs Status: RoHS non-compliant
• Core Processor: MCS 51
• Core Size: 8-Bit
• Speed: 24MHz
• Connectivity: SIO
• Peripherals: WDT
• Number Of I /o: 32
• Program Memory Size: 16KB (16K x 8)
• Program Memory Type: OTP
• Ram Size: 512 x 8
• Voltage - Supply (vcc/vdd): 4.5 V ~ 5.5 V
• Oscillator Type: External
• Operating Temperature: 0°C ~ 70°C
• Package / Case: 44-PLCC
• Eeprom Size: -
• Data Converters: -
• Other names: 807306

8XC51RA RB RC
ROM and EPROM Lock System
The program lock system when programmed pro-
tects the onboard program against software piracy
The 83C51RX has a one-level program lock system
and a 64-byte encryption table See line 2 of Table
5 If program protection is desired the user submits
the encryption table with their code and both the
lock-bit and encryption array are programmed by the
factory The encryption array is not available without
the lock bit For the lock bit to be programmed the
user must submit an encryption table
The 87C51RX has a 3-level program lock system
and a 64-byte encryption array Since this is an
EPROM device all locations are user-programma-
ble See Table 5
Encryption Array
Within the EPROM array are 64 bytes of Encryption
Array that are initially unprogrammed (all 1’s) Every
time that a byte is addressed during a verify 6 ad-
dress lines are used to select a byte of the Encryp-
tion Array This byte is then exclusive-NOR’ed
(XNOR) with the code byte creating an Encryption
Verify byte The algorithm with the array in the un-
programmed state (all 1’s) will return the code in its
original unmodified form For programming the En-
cryption Array refer to Table 4 (Programming the
EPROM)
When using the encryption array one important fac-
tor needs to be considered If a code byte has the
value 0FFH verifying the byte will produce the en-
cryption byte value If a large block (
code is left unprogrammed a verification routine will
display the contents of the encryption array For this
reason all unused code bytes should be pro-
grammed with some value other than 0FFH and not
all of them the same value This will ensure maxi-
mum program protection
Program Lock Bits
The 87C51RX has 3 programmable lock bits that
when programmed according to Table 5 will provide
different levels of protection for the on-chip code
and data
18
l
64 bytes) of
If any program lock bits were programmed erasing
the EPROM will not erase the program lock bits and
programming of the EPROM is disabled
Reading the Signature Bytes
The 8XC51RX has 3 signature bytes in locations
30H 31H and 60H To read these bytes follow the
procedure for EPROM verify but activate the control
lines provided in Table 4 for Read Signature Byte
Erasure Characteristics
(Windowed Packages Only)
Erasure of the EPROM begins to occur when the
chip is exposed to light with wavelength shorter than
approximately 4 000 Angstroms Since sunlight and
fluorescent lighting have wavelengths in this range
exposure to these light sources over an extended
time (about 1 week in sunlight or 3 years in room-
level fluorescent lighting) could cause inadvertent
erasure If an application subjects the device to this
type of exposure it is suggested that an opaque la-
bel be placed over the window
The recommended erasure procedure is exposure
to ultraviolet light (at 2537 Angstroms) to an integrat-
ed dose of at least 15 W-sec cm
EPROM to an ultraviolet lamp of 12 000
rating for 30 minutes at a distance of about 1 inch
should be sufficient
Erasure leaves all the EPROM Cells in a 1’s state
Location
30H
31H
60H
87C51RC
87C51RB
87C51RA
83C51RC
83C51RB
83C51RA
Device
All
All
2
Contents
42H C2H
41H C1H
40H C0H
Exposing the
C2H
C1H
C0H
89H
58H
W cm
2