Functional description 393
Micro Processing Unit (MPU)
The MPU, which is based on a Motorola 68020 processor, coordinates and
controls data transfer and port addressing, communicating via the CPU bus
with the system.Prioritized interrupts tell the MPU which tasks to perform.
Memory
The MSDL card contains two megabytes of Random Access Memory
(RAM) for storing downloaded peripheral software that controls MSDL port
operations. The MSDL card includes the shared RAM that is used as a
communication interface bufferbetween the CPU and the MPU.
The MSDL Flash Erasable Programmable Read Only Memory (Flash
EPROM) also includes the peripheral software to protect it against a power
failure or reset. MSDL can copy peripheral software directly from the Flash
EPROM after power up or reset instead of requesting that the system CPU
download it.
The MSDL card also contains Programmable Read Only Memory (PROM)
for firmware that includes the bootstrap code.
Serial interface
The MSDL card provides one monitor port and four programmableser ial
ports that can be configured for the following various interfaces and
combinations of interfaces:
•synchronous ports 0–3
•asynchronous port 0
•DCE or DTE equipment emulation mode
•RS-232 or RS-422 interface
Transmissionmode – All four ports of the MSDL can be configured for
synchronous data transmission by software. Port 0 can be configured for
asynchronous data transmission for CRT,TTY, and printer applications only.
Equipment emulation mode – Configure an MSDL port to emulate DCE
or DTE by setting switches on the card and downloadingLD 17 interface
parameters.
I/O port electrical interface – Each MSDL port can be configured as an
RS-232 or RS-422 interface by setting the switches on the MSDL card.
MSDL ports use Small Computer Systems Interface (SCSI) II 26-pin female
connectors.
Nortel Communication Server 1000
Circuit Card Reference
NN43001-311 01.04 Standard
Release 5.0 23May 2008
Copyright© 2003-2008, Nor tel Networks
.