Ether Board - NEC NC1600C Service Manual

Description of Operation of the ETHER Board Circuit
This board is an 8-Port swiching hub for 100BASE-TX and 10BASE-T.
1. VLAN
By the use of VLAN function of IC8300 (RTL8309SB) the board can function as 2-system switching hub,
each system having 4 independent ports.
Group A: M8501-M8504
Group B: M8505-M8507
Connection can freely made between each port within the groups; however, communication between the
groups is impossible.
This function can be set by the set data in EEPROM-IC8503(BR24C02) at the time of reset.
The board that permits communication between Groups A-B, therefore, cannot be set correctly from IC8503.
(IC8300 at default permits 8-port full communication.)
2. Auto MDI/MDI-X
This board can automatically detect the difference between straight and cross cables and switch between
them. Thus, twisted-pair cables to be connected can be any kind.
3. Power supply
As a power supply 5 volts is supplied from DIV PWB via connector POLAN (S2B-PH).
In IC8501 (PQ070XH02ZPH) 5 volts is regulated to 3.3 volts which is then supplied to IC8300 (RTL8309SB)
and IC8503 (BR24C02).
In IC8502 (PQ070XH02ZPH) 3.3 volts is regulated to 1.8 volt which is supplied to IC8300 (RTL8309SB).
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CIRCUIT DESCRIPTION
8-15