Intermec EasyCoder 501 Service Manual page 129

Chapter 17 CPU Board
17.3 Circuits and
Straps, cont.
128
IC-508 DMA Circuit
DMA stands for Direct Memory Access and it is supported by an
82C37A. Its purpose is to carry out a speedy shift out of data to
the thermal printhead. Upon reception of the start/stop addresses of
the location of data in RAM memory, it fetches the data, word by
word, and shifts them out. This procedure is faster than performed
by a processor due to the fact that no instructions are needed.
The DMA circuit just fetches the immediate data from one place
(RAM) and puts it into another (shift register).
IC-700 Program GAL
"GAL" is an acronym for Generic Array Logic. This is a pro-
grammed array containing a number of internal logical gates com-
bined in an application-specifi c pattern. It supplements the GAL
circuit on IC-04 (P/N 1-971805-xx, see above).
There are three types of GAL circuits for IC-700, one for Easy-
Coder 501 S, another for EasyCoder 501E and EasyCoder 501 SA,
and a third for EasyCoder 501 LinerLess. It is most important the
correct type of GAL is fi tted.
Printer Type
EasyCoder 501 S
EasyCoder 501 E & SA
EasyCoder 501 LL
FY-300 Fuse
The same type of fuse (6.3A 5 × 20 FST IEC) is used on all Easy-
Coder 501 printers, regardless of AC voltage.
P-9 Special Application Straps
This connector contains 7 pairs of pins, some of which are fi tted
with spare jumpers, and are mainly intended for special applica-
tions.
Important!
When no transfer ribbon mechanism is fi tted, a jumper must be
fi tted on the pair of pins marked "J-1" in order substitute the
signal from the missing ribbon-end sensor. Correspondingly, no
such jumper must be fi tted when the printer is fi tted with a transfer
ribbon mechanism.
P-10 +24V
This strap is used for checking the +24V voltage (V24).
Jumper fi tted.
Jumper removed:
Default:
GAL Part No.
1-971803-xx
1-971804-xx
1-971810-xx
+24V is ON
+24V is controlled by the processor
No jumper fi tted
Intermec EasyCoder 501 – Service Manual Ed. 7