Epson C117001-N - DFX 5000+ B/W Dot-matrix Printer Service Manual page 59

Operating Principles
5. The print data is stored in the line buffer in units of one line of data.
The CPU reads the print data stored in the line buffer byte by byte, accesses the CG (Character
6.
Generator), and expands the data in the image buffer (in the case of download characters, in
the download CG). A row of expanded data is output to the printhead control circuit as head
data.
7. When data is expanded to an italic or super/subscript character, the CPU uses IC7 to expand it
via MMIO.
8. The CPU controls the CR motor by calculating the control data for each line from the print data
in the line buffer. When a paper feed command is sent after one line is printed, the CPU
executes paper feeding.
For NLQ characters, printing one line consists of two passes; the printer performs steps 6 through 8
twice. When the CPU expands the data from the CG in the image buffer, it uses the 24-bit shift
register in IC7. The CPU is always ready to fetch data so printing can be viewed as an
interrupt-to-fetch operation. Whenever the input data buffer is not full between printing
operations, data is fetched. Table 2-3 describes the functions of the main printer components.
The data flow from the serial interface is the same as the data flow from the parallel
Note:
interface, described above, except the signal names and data access method differ.
Location
TMP96C141
(CPU)
PROM
SLA7026
NJM2903
SLA5007
2-20
Table 2-3. Main IC Functions
Receives data from the host computer via the gate array,
loads the data to the input buffer in PS-RAM, and converts the
image data to print data.
CR and PG motor pulse encoder l/O (input/output)
Contains the program that runs the CPU.
Holds the CPU working area and buffers
(input, line, and image buffers).
Drives the RF motor and controls the constant current.
Drives the PG motor.
Detects the current in the CR motor driver and feeds it back to
the gate away.
Drives the CR motor.
Functions
Rev. A