Specifications

Cache On
The ^CO (Cache On) instruction is used to change the size of the
character cache. By definition, a “character cache” (from here on
referred to as cache) is a portion of the DRAM reserved for storing
scalable characters. All printers have a default 22K cache that is
always turned on. The maximum single character size that can be
stored, without changing the size of the cache, is 450 dots x 450 dots.
There are two types of fonts used in Zebra printers: bitmapped and
scalable. Letters, numbers, and symbols in a bitmapped font have a
fixed size. For example 10 points, 12 points, 14 points, etc. On the
other hand, scalable fonts are not fixed in size. Their size is user
selectable.
Because their sized is fixed, bitmapped fonts can be moved quickly to
the label. By contrast, scalable fonts are much slower because each
character is built on an as-needed basis before it is moved to the label.
By storing scaled characters in a “cache” they can be recalled at a
much faster speed.
The number of characters that can be stored in the cache depends on
two factors; the size of the cache (memory) and the size of the charac-
ter (in points) being saved. The larger the point size, the more space
in the cache it uses. The default cache stores every scalable character
that is requested for use on a label(s). If the same character, with the
same rotation and size is used again, it is quickly retrieved from the
cache.
It is quite possible that after a while, the print cache could become
full. Once this happens space for new characters is obtained by elimi-
nating an existing character from the print cache. Existing characters
are eliminated by determining how often they have been used. This is
done automatically. For example, a 28 point “Q” that was used only
once would be a good candidate for elimination from the cache.
Maximum size of a single print cache character is 1500 dots x 1500
dots. It would require a cache of 300K for this.
When the cache is too small for the desired style, smaller characters may
appear but larger characters will not. If possible, increase the size of
the cache.
184 ZPL II COMMAND REFERENCE
^C O