Nortel Networks 553-3001-211 manual Micro Processing Unit MPU, Memory, Serial interface

Page 382 of 894 NT6D80 MSDL card

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 buffer between 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 programmable serial 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

Transmission mode – 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.

553-3001-211 Standard 2.00 September 2004