Owners Manual
2800 Series Marquee
2.8 Tutorial #5, Storing Messages in EEPROM Memory
If you have completed Tutorials 1 through 4, you now know enough to successfully use the 2800 in most
industrial applications. The typical setup is to program a PC or PLC to, monitor a production process, decide
what text the marquee(s) should display, and then send that text to the marquee(s) using the text entry command
demonstrated in tutorials 1 through 4. This works very well for displaying real time production status information,
but there are other ways we can operate the marquee.
2800 marquees have an EEPROM memory chip, allowing the marquee to store 242 messages, 32 characters
long each. The good characteristic of EEPROM memory, is that it is non-volatile. Data stored in the EEPROM
chip remains even in the absence of power.
The bad characteristic of EEPROM memory is that every time data is written to the chip, it accumulates a little bit
of wear. Typically it takes about 100,000 write operations to break the chip This behavior is similar to bending a
piece of metal. Each time the metal is bent, it accumulates a little bit of mechanical wear. Bend it enough times
and eventually the piece of metal will break.
The 100K write limit is not an issue when you change the text stored in the chip once a day. At one write
operation per day, it will take about 274 years to break the chip. But it is a major issue when you change the text
stored in the chip once per minute. At one write operation per minute, the chip could fail in as little as 69 days!
To store a message in EEPROM memory, first, send a text entry command to store a message in the marquee
text entry buffer. The example text entry command from tutorial #1 is diagrammed below.
Address Header Entry
Start
Message Text Literal Entry
End
CTRL-B A ESC H e l l o SPACE W o r l d CTRL-E
02h 41h 1Bh 48h 65h 6Ch 6Ch 6Fh 20h 57h 6Fh 72h 6Ch 64h 05h
Next send the message store command diagrammed below to copy the text entry buffer to stored message buffer
001. There are 242 stored message buffers in the EEPROM chip, numbered 001 to 242.
Address Header Entry
Start
Number
Start
Location Number Store
Msg
End
Entry
CTRL-B A ESC CTRL-N 0 0 1 CTRL-A CTRL-E
02h 41h 1Bh 0Eh 30h 30h 31h 01h 05h
The address header section gets the attention of the marquee. The entry start section tells the marquee to
prepare to receive an entry. The number start section tells the marquee that the entry will be a three digit location
number. The location number section supplies the three digit location number (001 to 242). The store message
section tells the marquee to copy the contents of the text entry buffer to one of the EEPROM stored message
buffers. The previously supplied location number specifies which stored message buffer to overwrite. The end
entry section tells the marquee that the entry is complete.
Be sure to store a message in EEPROM stored message buffers 001, and 002. We will use them in the next
tutorial. If you experiment, remember that the location numbers must always be exactly three numeric characters
and specify a location number between 001 and 242.
Advanced Feature: There actually is a stored message buffer 000, and you can change it using the store
message command, but be aware that this buffer has the special purpose of storing the default message. 2800s
automatically display the default message when there are no stored messages recalled, and the immediate
message buffer is empty. Before shipment, the factory sets the default message to “READY”, but you could
change it to something more fun, such as “Welcome to our factory!”.
Page 20 PB-2149-335B
(12 Seiten)
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