z8f083a ZiLOG Semiconductor, z8f083a Datasheet - Page 144

• Manufacturer Part Number: z8f083a
• Description: High-performance 8-bit Microcontrollers
• Manufacturer: ZiLOG Semiconductor

PS026308-1207
Note:
Optimizing NVDS Memory Usage for Execution Speed
As listed in
trade-off for minimizing the frequency of writes that require post-write page erases. The
NVDS read time of address N is a function of the number of writes to addresses other than
N since the most recent write to address N, as well as the number of writes since the most
recent page erase. Neglecting effects caused by page erases and results caused by the
initial condition in which the NVDS is blank, a rule of thumb is that every write since the
most recent page erase causes read times of unwritten addresses to increase by 0.8 μs, up
to a maximum of 258 μs.
Table 90.NVDS Read Time
For every 200 writes, a maintenance operation is necessary. In this rare occurrence, the
write takes up to 58 ms to complete.
If NVDS read performance is critical to your software architecture, you can optimize your
code for speed by using any of the methods listed below.
1. Periodically refresh all addresses that are used. This is the most useful method. The
2. Use as few unique addresses as possible. This helps to optimize the impact of
Operation
Read
Write
Illegal Read
Illegal Write
optimal use of NVDS in terms of speed is to rotate the writes evenly among all
addresses planned to use, bringing all reads closer to the minimum read time. Because
the minimum read time is much less than the write time, however, actual speed
benefits are not always realized.
refreshing.
Table
90, the NVDS read time varies drastically, this discrepancy being a
Minimum
Latency (
71
126
6
7
μs
)
Maximum
Latency (
258
136
6
7
μs
)
Z8 Encore!
Product Specification
Non Volatile Data Storage
®
F083A Series
132