PIC16HV540-20I/P Microchip Technology, PIC16HV540-20I/P Datasheet - Page 7

• Manufacturer Part Number: PIC16HV540-20I/P
• Description: IC MCU OTP 512X12 18DIP
• Manufacturer: Microchip Technology
• Series: PIC® 16Cr

Specifications of PIC16HV540-20I/P

• Core Processor: PIC
• Core Size: 8-Bit
• Speed: 20MHz
• Peripherals: Brown-out Detect/Reset, POR, WDT
• Number Of I /o: 12
• Program Memory Size: 768B (512 x 12)
• Program Memory Type: OTP
• Ram Size: 25 x 8
• Voltage - Supply (vcc/vdd): 3.5 V ~ 15 V
• Oscillator Type: External
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 18-DIP (0.300", 7.62mm)
• Processor Series: PIC16H
• Core: PIC
• Data Bus Width: 8 bit
• Data Ram Size: 25 B
• Maximum Clock Frequency: 20 MHz
• Number Of Programmable I/os: 12
• Number Of Timers: 8
• Operating Supply Voltage: 3.5 V to 15 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: Through Hole
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -
• Data Converters: -
• Connectivity: -
• Lead Free Status / Rohs Status: Details

3.0
The program code written into the EPROM can be pro-
tected by writing to the “CP” bit of the configuration
word. All memory locations starting at 0x40 and above
are protected against programming. It is still possible to
program locations 0x00 through 0x3F, the ID locations,
and the configuration word.
3.1
In a code protected part, these locations can still be
programmed. They will read back scrambled data. In
any event, the programmer cannot verify the device
once it is code protected.
In code protected parts, the contents of the program
memory cannot be read out in a way that the program
code can be reconstructed. A location when read out
will read as: 0000 0000 xxxx where xxxx is the XOR of
the three nibbles.
3.2
To allow portability of code, a PIC16HV54X programmer is required to read the configuration word and ID locations
from the hex file when loading the hex file. If configuration word information was not present in the hex file then a simple
warning message may be issued. Similarly, while saving a hex file, all configuration word and ID information must be
included. Configuration word should have the address of 0xFFF. ID locations are mapped at addresses described in
Section 1.6.1 and Table 3-1. An option to not include this information may be provided.
Microchip Technology Inc. feels strongly that this feature is important for the benefit of the end customer.
Note:
1999 Microchip Technology Inc.
CODE PROTECTION
Programming Locations 0x000 to
0x03F after Code Protection
Embedding Configuration Word and ID Information in the Hex File
Locations [0x000 : 0x03F] are not secure
after code protection.
For example, if the memory location contains 0xC04
(movlw 4), after code protection the output will be
0x008.
In addition, all memory locations starting at 0x40 and
above are protected against programming. It is still pos-
sible to program locations 0x000 through 0x03F and
the configuration word. However, performing a verify
with activated code protection logic puts a 4-bit wide
“checksum” on PORTA while the 8-bits of PORTB are
read as '0's. The checksum is computed as follows:
The four high order bits of an instruction word are
“XOR’ed” with the four middle and the four low order
bits, and the result is transferred to PORTA. All memory
locations are affected.
To program location 0x000 to 0x03F in a code pro-
tected part, the programmer should program one nibble
at a time and verify the result through the XOR’ed out-
put. For example, to program a location with 0xA93,
first program the location with 0xFF3, verify checksum
to be 0x003; then program the location with 0xF93 and
verify the XOR’ed output to be 0x00C and finally pro-
gram the location with 0xA93 and verify the read-out to
be 0x006.
PIC16HV54X
DS30467A-page 7