Epson RS-353, Service Manual

Page: 24 / 130

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ADB port
Features

10 kbps serial bus
*This interface supports a keyboard or a mouse.
*Mini DIN
connector
data communication is enabled.
a)
ADB port pin assignments
Figure 1- 29 Mini DIN 4-pin connector
Table 3 connector pin assignments
Pin
Signal Functions
1 ADB I/O data bus. This is the open collector signal pulled up to
through the 470 register on the main logicboard of a computer.
2 POWER ON In Macintosh II family this pin is connected to the pin 4 by the use of
some key on the ADB keyboard until this signal turns on the power.
In other models this pin is not connected.
3
output
4 GND
Ground
b) ADB port driving procedure
ADB device communicates with Mac through the protocol specified by Apple
computer Inc. which manipulates the level of ADB signals.
c) ADB port current limitation
Through the bus
current is supplied to ADB device. The total current consumed
by the device must
not exceed 500
(ex.) The current consumed by an ordinary mouse is approx. 20mA.
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