Functional Description

Programmable Clock

The IP2 chip implements a general purpose programmable clock output for external connection to the IndustryPacks. This feature complies with the STROBE function defined in the IndustryPack specification. The programmable clock’s clock source is the MC68060 bus clock. This clock input is fed through an 8-bit programmable pre-scaling counter whose output is fed to a 16-bit counter. The 16-bit counter increments at rising edges of the output of the pre-scale logic and clears every time it reaches the value programmed into the 16-bit programmable timer register. Depending on its programmed mode, the programmable clock output either pulses or toggles each time the 16-bit counter matches and clears. Additional control bits in the programmable clock control register allow software to stop, start, clear, and reverse the polarity of the programmable clock output. The programmable clock output’s programmable frequency range is from approximately 4 Hz to 16 MHz. The programmable clock logic also includes local bus interrupt control.

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Error Reporting

The following paragraphs describe the IP2 chip error reporting.

Error Reporting as a Local Bus Slave

The IP2 chip does not have the ability to assert the TEA* signal as a local bus slave. Because of this, the only bus error cycles that should ever be encountered when accessing to or through the IP2 chip are those that come from an external local bus timer due to no response from an IndustryPack. Note that any external local bus timer should be set for no less than 5 microseconds to allow for normal accesses to the slowest IndustryPack.

Error Reporting as a Local Bus Master

The IP2 chip does not connect to the ST1 and ST0 signal lines. Consequently, when it receives a TEA* termination to any cycle for which it is local bus master, no status will be available to indicate the source of the bus error. There is a status bit in each DMAC status register which

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Motorola MVME172 manual Programmable Clock, Error Reporting, Following paragraphs describe the IP2 chip error reporting