HP 330 Service Information Manual page 119

Frontplane circuits include the LAN chip set, timer, and the transceiver chip. The LAN chip set
serves the dual function of a DMA controller and an Ethernet/EEEE 802.3 controller. Encoded
data from the SIA is transmitter by the transceiver chip. Data from the network is sent by the
transceiver chip to the SIA.
The LAN portion of the board is software compatible with the HP 98643 LAN/300 Link Card.
Eight DIP switches on the system interface board control the following LAN functions:
• Select Code, 0 through 3l.
• Interrupt Level, 3 through 6.
• Local/Rernote.
Switches for LAN interface configuration are explained Table 3-8. Refer to the picture of the
system interface board, Figure 3-22 for its location.
RS-232 Interface
An RS-232 Interface section is part of the system interface board's electronics. Using an INS8250
UART, it's almost identical to the HP 98644A RS-232 Serial Interface Card. It differs from the
HP 98644A Interface Card in that it:
• Allows interrupts at level 5 only. There are no switches to change the interrupt level is
the same as the HP 98644 Card.
• Permanently sets the select code to 9. The HP 98644 card has switches which allow this
address to be changed.
• Does not allow reconfiguration to change the RS-232's ID to that of the HP 98626 card.
Three switches on the system interface board are associated with RS-232. Located on the
HPIB/RS232 configuration switch, they perform the following functions:
• REM - Controls the local/remote bit in the ID register.
• MEN -- Sets the handshake input lines to their default condition, all ones.
• DIS -- Disables the RS-232 at select code 9 so it won't be found. all ones.
In addition to the registers built into the INS8250 UART, two external register have also been
implemented. Both sets of registers are multi-mapped within a 64 Kbyte region of memory
associated with I/O select code 9.
Functional Description
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