Address Decoding - Nortel Circuit Card Installation Manual

Page 398 of 906
Card mix

Address decoding

Port specifications
553-3001-211 Standard 3.00
NT6D80 MSDL card
A system that exclusively uses MSDL cards can support up to 16 such cards,
providing 64 ports. These ports can be used to run various synchronous and
asynchronous operations simultaneously.
The system will also support a mix of interface cards (MSDL, DCHI, and
ESDI for example). However, using multiple card types will reduce the
number of cards and ports available.
The MSDL card decodes the full address information received from the
system. This provides 128 unique addresses. Since MSDL ports
communicate with the CPU using a single card address, the system can
support 16 MSDL cards providing 64 ports.
The MSDL card addresses are set using decimal switches located on the card.
These switches can select 100 unique card addresses from 0 to 99.
An address conflict may occur between the MSDL and other cards because of
truncated address decoding by the other cards. For example, if a DCHI port
is set to address 5, its companion port will be set to address 4, which means
that none of the MSDL cards can have hexadecimal address numbers 05H,
15H, ...75H, nor addresses 04H, 14H, ...74H. To avoid this conflicts system
software limits the MSDL card addresses from 0 to 15.
The MSDL card provides four programmable serial ports configured with
software as well as with switches for the following modes of operation:
Transmission mode Configure an MSDL port for synchronous or
asynchronous data transmission using LD 17.
Synchronous transmission uses an external clock signal fed into the MSDL.
August 2005