Introduction - Motorola MVME1X7P Programmer's Reference Manual

4MCECC Functions
4

Introduction

The ECC DRAM Controller ASIC (MCECC) is a device used on earlier
MVME167/177 models whose functions are now incorporated into the
Petra chip on the MVME1x7. The two memory controllers modeled in
Petra duplicate the functionality of the "parity memory controller" found
in MC ASICs as well as that of the "single-bit error correcting/double-bit
error detecting" memory controller found in MCECC ASICs.
For ease of use in conjunction with processes, programming models and
documentation developed for earlier boards, the structure of this manual
preserves the functional distinctions that formerly characterized the
MCECC ASIC. This chapter describes the Petra chip as used in the
MVME1x7 MCECC implementation.
The MCECC ASICs, used in a set of two, provided the interface to a 144-
bit wide DRAM memory array. The Petra implementation provides an
interface to a 40-bit SDRAM memory array. There are 32 bits for data, 7
for check bits, and one bit that is not used. SDRAM configurations that
allow array sizes of 16MB to 128MB are supported. For a complete
description of the memory configurations that are supported, refer to the
definition of the SDCFG2-SDCFG0 bits in the SDRAM Configuration
register.
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