Motorola MVME162 manual Data Bus Structure, MC68040 or MC68LC040 MPU, No-VMEbus-Interface Option

Functional Description 1

Data Bus Structure

The local data bus on the MVME162 is a 32-bit synchronous bus that is based on the MC68040 bus, and which supports burst transfers and snooping. 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: 82596CA LAN, 53C710 SCSI, VMEbus, and MPU. Generally speaking, any master can access any slave; however, not all combinations pass the common sense test. Refer to the MVME162 Embedded Controller 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.

MC68040 or MC68LC040 MPU

The MC68040 or MC68LC040 processor is used on the MVME162. The MC68040 has on-chip instruction and data caches and a floating point processor. The major difference between the two processors is that the MC68040 has a floating point coprocessor. Refer to the M68040 Microprocessor User’s Manual for more information.

MC68xx040 Cache

The MVME162 local bus masters (VMEchip2, MC68xx040, 53C710 SCSI controller, and 82596CA Ethernet controller) have programmable control of the snoop/caching mode. The MVME162 local bus slaves which support MC68xx040 bus snooping are defined in the Local Bus Memory Map table later in this chapter.

No-VMEbus-Interface Option

The MVME162 can be operated as an embedded controller without the VMEbus interface. To support this feature, certain logic in the VMEchip2 has been duplicated in the MCchip. This logic is inhibited in the MCchip if the VMEchip2 is present. The enables for these functions are controlled by software and MCchip hardware initialization.

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