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VMEchip2

In addition to the VMEbus timer, the chip contains a local bus timer. This timer asserts the local TEA when the local bus cycle maintained in its asserted state for longer that the programmed time-out period. This timer can be enabled or disabled under software control. The time-out period can be programmed for 8, 64, or 256 secs.

Reset Driver

The chip 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 RESET switch, a power up reset, a watch dog time-out, or by a control bit in the LCSR. SYSRESET remains asserted for at least 200 msec, as required by the VMEbus specification.

Similarly, the chip provides an input signal and a control bit to initiate a local reset operation.

The local reset driver is enabled even when the chip is not the system controller. A local reset may be generated by the RESET switch, a power up reset, a watch dog time-out, a VMEbus SYSRESET, or a control bit in the GCSR.

Local Bus Interrupter and Interrupt Handler

There are 31 interrupt sources in the VMEchip2: VMEbus ACFAIL, ABORT switch, VMEbus SYSFAIL, write post bus error, external input, VMEbus IRQ1 edge-sensitive, VMEchip2 VMEbus interrupter acknowledge, tick timer 2-1, DMAC done, GCSR SIG3-0, GCSR location monitor 1-0, software interrupts 7-0, and VMEbus IRQ7-1. Each of the 31 interrupts can be enabled to generate a local bus interrupt at any level. For example, VMEbus IRQ5 can be programmed to generate a level 2 local bus interrupt.

The VMEbus AC fail interrupter is an edge-sensitive interrupter connected to the VMEbus ACFAIL signal line. This interrupter is filtered to remove the ACFAIL glitch which is related to the BBSY glitch.

The SYS fail interrupter is an edge-sensitive interrupter connected to the VMEbus SYSFAIL signal line.

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Motorola MVME172 manual Local Bus Interrupter and Interrupt Handler, Reset Driver