RELIANCE 45C307 Network communication module

The MVME177 provides SCSI terminator power through a diode and a 1 amp polyswitch F1 located on the P2 Adapter Board. If the polyswitch is blown (i.e., open), the SCSI devices may not operate or may function erratically. When the P2 Adapter Board is used with an MVME712M and the SCSI bus is connected to the MVME712M, the green LED (DS2) on the MVME712M front panel lights when there is SCSI terminator power. If the LED flickers during SCSI bus operation, the polyswitch should be checked.

This chapter provides necessary information to use the MVME177 module in a system configuration. This includes: 

❏ Controls and indicators 

❏ Memory maps 

❏ Software initialization of the module

ABORT Switch S1

 When enabled by software, the recessed front panel ABORT switch generates an interrupt at a user-programmable level. It is normally used to abort program execution and return to the 177Bug debugger firmware located in the MVME177 EPROMs. The ABORT switch interrupter in the VMEchip2 is an edge-sensitive interrupter connected to the ABORT switch. This interrupter is filtered to remove switch bounce.

SYSRESET* remains asserted for at least 200 msec, as required by the VMEbus specification. Similarly, the VMEchip2 provides an input signal and a control bit to initiate a local reset operation. By setting a control bit, software can maintain a board in a reset state, disabling a faulty board from participating in normal system operation.

RESET Switch S2 

The recessed front panel RESET switch resets all onboard devices, and drives SYSRESET* if the board is system controller. The RESET switch may be disabled by software. The VMEchip2 includes both a global and a local reset driver. When the chip operates as the VMEbus system controller, the reset driver provides a global system reset by asserting the VMEbus signal SYSRESET*. A SYSRESET* may be generated by the following: ❏ RESET switch 

❏ Power up reset 

❏ Watchdog timeout 

❏ Control bit in the LCSR

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