UBI EasyCoder 501 SA, Руководство по обслуживанию

Страница: 115 / 214

UBI EasyCoder 501 – Service Manual
115
17.3
Circuits and Straps, cont'd.
17. CPU BOARD, cont'd.
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 for
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
combined in an application-specific pattern. It supplements the
GAL circuit on IC-04 (article No. 1-971805-xx, see above).
There are two types of GAL circuits for IC-700, one for EasyCoder
501 and another for EasyCoder 501E and EasyCoder 501 SA. It is
most important the correct type of GAL is fitted.
Printer Type GAL Article No.
EasyCoder 501 1-97180 3 -xx
EasyCoder 501 E 1-97180 4 -xx
EasyCoder 501 SA 1-97180 4 -xx
FY-300 Fuse
The same type of fuse (6.3A 5
×
20 FST IEC) is used on all
EasyCoder 501 printers, regardless of mains voltage.
P-9 Special Application Straps
This connector contains 7 pairs of pins, some of which are fitted
with spare jumpers, and is mainly intended for special applications.
Important!
When no transfer ribbon mechanism is fitted, a jumper must be
fitted 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 fitted when the printer is fitted with a transfer ribbon
mechanism.
P-10 +24V
This strap is used for checking the + 24V voltage (V24).
Jumper fitted.
+ 24V is ON
Jumper removed: + 24V is controlled by the processor
Default: No jumper fitted
Continued!