The RadiSys EXM-16 is a SCSI controller module designed for mass storage connectivity within embedded PC (EPC) systems. It connects via a 116-pin card-edge EXM expansion connector and operates on an electrically ISA-compatible 16-bit local bus interface. The module supports DMA channels DRQ0 through DRQ6, with DRQ0–3 handling 8-bit transfers and DRQ5–6 handling 16-bit transfers. Fifteen dedicated GND lines enhance noise immunity, while an inverted RESET signal improves signal integrity. Configuration registers are addressable at I/O addresses 100h, 102h, and 103h via the EXMID signal.
Technical Specifications
• Bus Interface: 16-bit EXM expansion interface, electrically similar to PC ISA bus
• SCSI Controller: Mass storage connectivity module for embedded systems
• DMA Support: DRQ0–DRQ6 available; DRQ0 highest priority; DRQ4 reserved for system board
• DMA Transfer Modes: 8-bit on DRQ0–DRQ3; 16-bit on DRQ5–DRQ6; DRQ7 unavailable
• Configuration Registers: Addressable at 100h, 102h, 103h in local I/O space
• Ground Lines: 15 dedicated GND connections for noise immunity
• Connector: 116-pin card-edge rear connector
– Key Features
• Modular expansion supporting up to 8 modules per EPC chassis
• ISA-compatible software execution without modification
• Inverted RESET signal for improved noise margin
• Local I/O expansion independent of industrial bus, avoiding performance bottlenecks
• Standardized EXM interface released to public domain October 1989
– Typical Applications
Industrial embedded systems requiring local mass storage control. Multi-module configurations in space-constrained environments. Legacy PC-based control systems migrated to embedded architectures.
– Compatibility & Integration
Designed for EPC chassis supporting the EXM expansion interface. Compatible with VME, VXI, and EMC system form factors. Standard PC software executes without modification due to ISA bus electrical equivalence. Does not support ISA busmasters.
