Schweitzer Engineering Laboratories SEL-2020 - Page 347

Date Code 20010518 Appendix E E-3
SEL-2020 Instruction Manual
* Only applies to SEL-321-1 relays with a date code later than 950907. Older SEL-321-1 relays have same
sizes as SEL-321 relays.
** Only available in SEL-587 relays with a date code later than 950907.
*** Only applies to SEL-501 relays with a date code later than 960101.
To determine the Flash memory required, perform the following steps, using Table E.3 as a
planning sheet:
1. Estimate the desired maximum number of records (n) of each type on each port.
2. For “20” message archive regions, determine the memory requirements using the records
estimated as “n” in Table E.1. For regions in which you use generic parsing, follow the
process in Table E.2 to find the archive requirements.
3. Calculate the blocks required per region (rounding all fractions up to the nearest integer)
and enter in Table E.3. Sum to determine total requirement.
4. If total requirement exceeds 8192 blocks, you must use more than one SEL-2020, or
reduce the amount of data you archive.
Table E.2: Generic Parsing Archive Requirements
a) If you are using CHAR_STRING parsing, each record will require S=28+NUM bytes
where NUM is your size setting for the region. If you are using INT_STRING or
ASCII_INT parsing, each record will require S=28+2⋅NUM bytes. If you are using
ASCII_FLOAT parsing, each record will require S=28+4⋅NUM.
b) If the size determined in bytes is greater than 254, the number of blocks required per
record is the record size in bytes plus 2 divided by 256 and rounded up:
A
S
=
+
é
ê
ê
ù
ú
ú
2
256
c) If the size determined in bytes is less than 128, the number of records that will fit in a
block is 254 divided by the record size and rounded down:
A
S
=
ê
ë
ê
ú
û
ú
1
254
d) If the size determined is greater than 128 bytes and less than 254, you will get one record
per block:
A = 1
e) The archive memory requirements are:
An+1