Prevention Hosts From Data Transfer Time-Out - Epson Stylus Color 400 Service Manual

Chapter1 Product Description
[Signal level: TTL compatible (IEEE-1284 level 1 device)]
Parameter
VOH*
VOL*
IOH*
IOL
CO
VIH
VIL
IIH
IIL
CI
*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.
Figure 1-9. Parallel Interface Timing Chart(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.
1-18
Table 1-14. Signal Level
Minimum Maximum
--- 5.5V
-0.5V
--- 0.32mA
--- 12mA
--- 50pF
--- 2.0V
0.8V
--- 0.32mA
--- 12mA
--- 50pF
Condition
---
VOH = 2.4V
VOL = 0.4V
---
VIH = 2.0V
VIL = 0.8V
Rev. A