Epson Stylus Color 640 Service Manual page 30

EPSON Stylus Color 440/640/740
Table 1-14. Typical Tack Timing
Parallel I/F Mode
High speed
Normal speed
Table 1-15. Signal level for TTL (IEEE-1284 level 1 device)
Parameters Minimum
VOH* ---
VOL* -0.5V
IOH* ---
IOL ---
CO ---
VIH ---
VIL 0.8V
IIH ---
IIL ---
CI ---
NOTE: A low logic level on the Logic H signal is 2.0V or less when the printer is
powered off and this signal is equal or exceeding 3.0V when the printer is
powered on. The receiver shall provide an impedance equivalent to 7.5K ohm
to ground.
1.3.2.1 Prevention Hosts from Data Transfer time-out
Generally, hosts abandon data transfer to peripherals when a peripheral
is in the busy state for dozens of seconds continuously. To prevent
hosts this kind of time-out, the printer receives data very slowly, several
bytes per minute, even if the printer is in busy state. This showdown is
started when the rest of the input buffer becomes several hundreds of
bytes. Finally, the printer is in the busy state continuously when the
input buffer is full.
Chapter 1 Product Description
Typical Tack Timing
2us (for Stylus Color 440,640)
1us (only for Stylus Color 740)
4us (for Stylus Color 440,640)
3us (only for Stylus Color 740)
Maximum COndition
5.5V
---
0.32mA VOH = 2.4V
12mA VOL = 0.4V
50pF
2.0V
---
0.32mA VIH = 2.0V
12mA VIL = 0.8V
50pF
1.3.2.2 Auto Interface Selection (for Stylus Color 640, 740)


Manual Selection:
One of two interfaces can be selected by the default setting mode.


Automatic Selection:
The automatic interface selection is enabled by the default setting
mode. In this automatic interface selection mode, the printer is
initialized to the idle state scanning which interface receives data
when it is powered on. Then the interface that receives data first is
selected. When the host stops data transfer and the printer is in the
stand-by state for the seconds, the printer is returned to the idle
state. As long as the host sends data or the printer interface is busy
state, the selected interface is let as it is.
Following explains conditions of other interfaces when a particular
interface is selected.

When the parallel interface is not selected, the interface gets
into BUSY state. At this time, LH signal is set to "L". That means
blocking power supply and no responds from 1284. Therefore, it
is necessary for the host, which requires Reverse transfer, to
check LH state.

When the serial interface is not selected, the interface sets the
DTR signal MARK.

When the printer is initialized or returned to the idle state,
Parallel interface becomes the ready condition and DTR of serial
interface becomes SPACE (Low) condition and reset off-line bit
of Main Status Register (MNSTS)to, option interface.
Revision A
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