![](/images/new-backgrounds/1147353/14735321x1.webp)
Functional Modes of Operation (Continued)
Security Level 2
This security level prevents programming of the
Security Level 1
This security level prevents programming of the
Security Level 0
This security level prevents programming of the
An erasure system should be calibrated periodically. The distance from lamp to unit should be maintained at one inch. The erasure time increases as the square of the distance. (If distance is doubled the erasure time increases by a factor of 4.) Lamps lose intensity as they age. When a lamp is changed, the distance has changed or the lamp has aged, the system should be checked to make certain full erasure is occurring.
Incomplete erasure will cause symptoms that can be mis- leading. Programmers, components, and even system de- signs have been erroneously suspected when incomplete erasure was the problem.
Minimum HPC167064 Erasure Time
Light Intensity | Erasure Time |
(Minutes) | |
15,000 | 36 |
|
|
10,000 | 50 |
|
|
Memory Map of the HPC167064
The HPC167064 has 256 bytes of
The ECON6 contains two bits ROM0 and RAM0. When these bits are ‘‘1’’ (erased default), full 16 kbytes of ROM and 512 bytes of RAM are enabled. Programming a ‘‘0’’ to these bits disables the lower 8k for the EPROM and upper 256 bytes for the RAM. The ECON registers are only acces- sible to the user during EPROM mode.
EPROM mode. Such accesses will return data value ‘‘FF’’ hex. Runtime Memory Protection is enforced as in security level 1.
These four levels of security help ensure that the user EPROM code is not tampered with in a test fixture and that code executing from RAM or external memory does not dump the user algorithm.
Erasure Characteristics
The erasure characteristics of the HPC167064 are such that erasure begins to occur when exposed to light with wave- lengths shorter than approximately 4000 Angstroms
After programming, opaque labels should be placed over the HPC167064’s window to prevent unintentional erasure. Covering the window will also prevent temporary functional failure due to the generation of photo currents.
The recommended erasure procedure for the HPC167064 is exposure to short wave ultraviolet light which has a wave- length of 2537 Angstroms
The HPC167064 should be placed within 1 inch of the lamp tubes during erasure. Some lamps have a filter on their tubes which should be removed before erasure. The era- sure time table shows the minimum HPC167064 erasure time for various light intensities.
Address In
EPROM Mode
7FFF
4000
3FFF
2000
1FFF
0000
Address In Other HPC Modes
Operation
FFFF
E000 –
DFFF
Enabled or Disabled by config logic
C000
11