Epson Stylus pro 7700m, Service Manual

Page: 50 / 139

2.3.2.6 DMA Controller
Data from the host computer is received automatically by the STB signal via the external Centronics interface.
The data is input to the input buffer on the DRAM (IC5). At this time, E05B09 detects the rising edge of the
external STB signal and outputs the STBDMA (strobe DMA request) signal to the CPU. When the CPU
detects this signal, the DMA controller in the CPU sends a bus request to the bus controller in the CPU, and
then the CPU releases the bus line.
Because of this, the external data is transported into the memory,
bypassing the CPU.
Common Driver
E05B09 (IC2 )
B P W C
B P W D
B L A T
B C L K
B C L K I N
B S O
C P W C
C P W D
C L A T
C C L K
C C L K I N
C S O
1 3
1 4
1 9
1 8
1 7
2 0
1 5
1 6
2 3
2 2
2 1
2 4
Common Driver
C O M 1 - 8
CO M1 - 6
SED5620 D (U1)
CN
1
1
CN
1
6 8
L A T
6 9
6 7
CN
1
1
CN
1
C L K
S I
L A T
C L K
S I
6 8
6 9
6 7
DO64 -49
DO48 -33
D O 32- 1 7
D O 16 - 1
Ro w A
R o w B
R o w C
R o w D
DO64 -49
D O 48- 3 3
D O 32- 1 7
DO16 -1
Row R (Mag enta )
Row S (Cyan)
Row T (Yellow)
Not C onnec t ed
C1 6 4 M AI N
O n Carriage (Head Driver B oard)
SED5620D (U2)
Figure 2-25. Printhead Drive Circuit Block Diagram
BAC DMAC
BAREQ
E05B09 (IC2)
S T B
S T B D M A
CPU H8 (IC1)
A C K
BUSY
D R E Q 1
9 129
Memory
D M A R Q
128 14
D R E Q 2
Figure 2-26. DMA Controller Operation
Operating Principles Stylus Pro Service Manual
2-20 Rev.A