The MVME147 MPU VMEmodule contains a port to the Small Computer
Systems Interface (SCSI) bus. The hardware interface is the WD33C93 SCSI
To relieve you of having to follow SCSI bus protocol, the SCSI firmware allows
you to pass commands to the bus through high level command packets.
Standard command packets are furnished, as well as custom SCSI sequence
packets that you may easily modify to fit particular applications. With this
method, the firmware interface can greatly speed up your software
The SCSI firmware resides in two 128K x 8 EPROMs and is co-resident with
MVME147Bug, the debug monitor for the MVME147 MPU VMEmodule.
The SCSI firmware offers the following features:
❏ Custom SCSI sequence packets that allow creation of customized
❏ TARGET role
❏ Multitasking -- up to 64 concurrent peripheral devices
❏ High level support of SCSI devices
❏ Interrupt mode allows real-time applications
❏ Polled mode -- non-interrupt operation
❏ DMA with memory/scatter/gather
❏ Multiple-user interface allows concurrent operation through independent
❏ Six entry points
❏ Thirty-one "canned" or standard function packets
Modes of Operation
When using the SCSI firmware, you have a choice of two modes of operation:
Interrupt mode and polled mode.