B&R Industries Provit 5000 User Manual - page 149
148
Provit 5000 User’s Manual
Controllers • Lifespan of Silicon Disks (Compact Flash, PC Card)
1. Calculations of the sectors
User sectors (system data): 20 * 1,024,000 byte / 512 byte = 40,000 sectors (are not changed)
User sectors:
20 * 1,024,000 byte / 512 byte = 40,000 sectors
Spare sectors:1% of user sectors = 800 Sectors
2. Write cycles per year
3 sectors per minute (2 FAT + 1 directory) are always upgraded.
(2 + 1) sectors * 60 minutes * 24 hours * 365 days = 1,576,800 write cycles per year.
3. Possible number of write/erase cycles per year
3 user sectors + 800 spare sectors = 803 sectors
803 sectors * 300,000 accesses = 240,900,000 write/erase cycles per year
4. Lifespan
The lifespan is then determined by 2 factors:
a) Memory capacity depleted (20 kByte are continually written)
20 MByte application memory / 20 kByte per minute = 16.67 hours
b) Spare sectors depleted (3 sectors are continually specified)
240,900,000 write erase cycles per year / 1,576,800 write cycles per year = a guaranteed
lifespan of 152.8 years
Typical lifespan: 152.8 years * 3.3 = 504.24 years
Because of the amount of data written every minute, the memory capacity is depleted
before the lifespan is reached, and no further data can be saved.