Manual

Page 19
The
uple
ime.
read
a PC
nlike
n not
cter-
pro-
ptic,
pro-
type
con-
ntee
vice.
point
s off
When
per-
One
per-
er of
bout
ry to
and,
If you think about how long it would take a million changes to the control program-
ming through the front key pad, you will see that it would take a very long time to get
to use up the life of the EEPROM.
Adding one of the computer communications options (e.g. 992, 993) changes the
picture. The speed of computer communications is such that hundreds of instruc-
tions can be made in less than a minute. In such a situation, the million erase/write
cycles could be used up in a couple of months causing the control to fail.
Usually in such a situation, the control is under close observation by the host com-
puter. It may not be necessary, then to the data written to the EEPROM, as it is ‘tran-
sitory’ in nature (changing set points for a ramp/soak sequence for example).
All 16A Series controls with communications options made before April 2001 are
only able to write to the EEPROM. Controls manufactured after this date have a
menu item in the Secure menu (
Stor) that allows the serial communications to write
to RAM (Stor = no) with a special write command that allows to EEPROM to be
updated or written directly to EEPROM (protocol command 0442).
The factory default is ‘write to EEPROM’ (Stor = YES).
If your computer system will be making frequent changes to the control we strongly
recommend that you select the ‘write to RAM’ parameters (Stor = no). If you are pri-
marily reading from the control, there is no need to change the setting.
Any instruments equipped with any Serial Communications are limited
to one million WRITE cycles to the EEPROM through the Serial
Communications Port. Exceeding this limit will generate a
F A 1 L tES t error. There is no limit to the number of times you can
READ from this instrument EEPROM.
Make sure that the software you use does not write too often to the instrument.
If you have any questions regarding how your software works with the instrument(s),
contact your System Administrator, Programmer, or Software Supplier.
949-1265:Layout 1 1/25/11 10:22 AM Page 19