DS87C550-QCL+ Maxim Integrated Products, DS87C550-QCL+ Datasheet - Page 32

• Manufacturer Part Number: DS87C550-QCL+
• Description: IC MCU EPROM ADC/PWM HS 68-PLCC
• Manufacturer: Maxim Integrated Products
• Series: 87Cr

Specifications of DS87C550-QCL+

• Core Processor: 8051
• Core Size: 8-Bit
• Speed: 33MHz
• Connectivity: EBI/EMI, SIO, UART/USART
• Peripherals: Power-Fail Reset, PWM, WDT
• Number Of I /o: 55
• Program Memory Size: 8KB (8K x 8)
• Program Memory Type: OTP
• Ram Size: 1K x 8
• Voltage - Supply (vcc/vdd): 4.5 V ~ 5.5 V
• Data Converters: A/D 6x10b
• Oscillator Type: External
• Operating Temperature: 0°C ~ 70°C
• Package / Case: 68-LCC, 68-PLCC
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -

DS87C550 EPROM High-Speed Microcontroller with ADC and PWM
unprogrammed (FFh). Once the Encryption Array is programmed in a non-FFh state, the verify value will
be encrypted.
For encryption to be effective, the Encryption Array must be unknown to the party that is trying to verify
memory. The entire EPROM also should be a non-FFh state or the Encryption Array can be discovered.
The Encryption Array is programmed as shown in Table 10. Note that the programmer cannot read the
array. Also note that the verify operation always uses the Encryption Array. The array has no impact
while FFh. Simply programming the array to a non-FFh state will cause the encryption to function.
EPROM ERASURE CHARACTERISTICS
Erasure of the information stored in the DS87C550’s EPROM occurs when the isolated gate structure of
the EPROM stage element is exposed to certain wavelengths of light. While the gate structure is to some
degree sensitive to a wide range of wavelengths, it is mostly wavelengths shorter than approximately
4,000 angstroms that are most effective in erasing the EPROM. Since fluorescent lighting and sunlight
have wavelengths in this range, they can cause erasure if the device is exposed to them over an extended
period of time (weeks for sunlight, years in room-level fluorescent light). For this reason (and others
mentioned previously), it is recommended that an opaque covering be placed over the window of the -K
(windowed PLCC) package type.
For complete EPROM erasure, exposure to ultraviolet light at approximately 2537 angstroms to a dose of
2
15W-sec/cm
at minimum is recommended. In practice, exposing the EPROM to an ultraviolet lamp of
2
12,000uW/cm
rating for 20 to 39 minutes at a distance of approximately 1 inch will normally be
sufficient.
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