Motorola MVME187 manual Data Bus Structure, M88000 MPU, Local Bus Arbitration

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Board Level Hardware Description

Data Bus Structure

The local data bus on theMVME187 is a 32-bit synchronous bus based on the MC68040 bus, and supports burst transfers and snooping.

Local Bus Arbitration

The various local bus master and slave devices use the local bus to communicate.

The local bus is arbitrated by priority type arbiter and the priority of the local bus masters from highest to lowest is:

1.82596CA LAN (highest)

2.CD2401 serial (through the PCCchip2)

3.53C710 SCSI

4.VMEbus

5.MPU (lowest)

In general, any master can access any slave; however, not all combinations pass the Òcommon sense test.Ó Refer to the Single Board Computers Programmer's Reference Guide and to the user's guide for each device to determine its port size, data bus connection, and any restrictions that apply when accessing the device.

M88000 MPU

The MVME187 is based on the M88000 family and uses one

MC88100 MPU and two MC88200 or MC88204 CMMUs.

One CMMU is used for the data cache and one is used for the instruction cache.

More information is available in the MC88100 and MC88200 user's manuals and the MC88204 data sheet.

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