Epson Stylus Color 400, Service Manual

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Chapter1 Product Description
Rev. A
1-18
[Signal level: TTL compatible (IEEE-1284 level 1 device)]
Parameter Minimum Maximum Condition
VOH* --- 5.5V
VOL* -0.5V ---
IOH* --- 0.32mA VOH = 2.4V
IOL --- 12mA VOL = 0.4V
CO --- 50pF
VIH --- 2.0V
VIL 0.8V ---
IIH --- 0.32mA VIH = 2.0V
IIL --- 12mA VIL = 0.8V
CI --- 50pF
*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.
[Data Transmission Timing for Reverse Channel]
The figure below shows timing chart of Parallel Interface Reverse channel.
1.3.3 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.
Table 1-14. Signal Level
Virtual Busy Status
Virtual Busy Status
Figure 1-9. Parallel Interface Timing Chart(Reverse Channel)