Nortel Networks 553-3001-211 Main memory, Shared memory, Flash Eprom memory, Eeprom memory

Page 776 of 894 NTBK51 Downloadable D-channel Handler daughterboard

Main memory

The main 68EC020 system memory is comprised of 1 Mbyte of SRAM and is accessible in 8 or 16 bits. The software, base code and application reside in main RAM and is downloaded from the software through the shared memory.

Shared memory

The shared memory is the interface between the CPU and the 68EC020 MPU. This memory is a 16 Kbyte RAM, expandable to 64 kbytes and accessible in 8 or 16 bits.

EPROM memory

The Bootstrap code resides in this 27C1000 EPROM and is executed on power up or reset.

Flash EPROM memory

Flash EPROM provides non-volatile storage for the DDCH loadware which minimizes the impact to sysload. The Flash EPROM provides an increase in system service with a reduced delay after a brown-out, and faster testing of a hardware pack after it is plugged in.

EEPROM memory

The DDCH uses a 1024 bit serial EEPROM for storing the Nortel Networks product code and a revision level. This information can be queried by the software.

Serial communication controller

The serial controller is the Zilog Z16C35 and is referenced as the Integrated Controller (ISCC). The ISCC includes a flexible Bus Interface Unit (BIU) and four Direct Memory Access (DMA) channels, one for each receive and transmit. The DMA core of the ISCC controls the data transfer between local RAM and the communication ports.

553-3001-211 Standard 2.00 September 2004