Epson DLQ-3000+, Service Manual

Page: 81 / 262

Operating Principles
Rev. A
2-19
2.3.3 Memory Back-up Circuit
When the printer power is turned off, mainly the following data is backed up in the EEPROM
AT93C66 (IC23).
Paper length, TOF, TEAR OFF, left and right margins, line spacing, pitch
selection, character code, character fonts, high speed print, print direction,
customer code
Interface setting
Values used for controlling the mechanism (condition for all the sensors)
Adjusted values used for controlling the mechanism (i.e. Bi-D adjustment, PG
adjustment and PG value)
IPD ID for the boot strap program
The first operation date, accumulated print amount, accumulated power-on time
and timing for ribbon replacement
Data to be backed up is transferred by the gate array as serial data. At printer power off, the
gate array outputs the chip select signal ESC from port 126 and data to be backed-up is sent
to the EEPROM from port 124 (EDO) before the power supply voltage completely drops. The
data stored in the EEPROM is read by sending data to the EDI terminal in the gate array
when the printer is turned on. ECK is the clock signal for synchronization.
C S
D I
D O
E E P R O M
A T 9 3 C 6 6
S K
E C K
E C S
E D I
E D O
E 0 5 B 4 6
G a t e A r r a y
Figure 2-14.Memory Back-up Circuit Block Diagram