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Documentation and Software Support

See the Downloads page for documentation on uM-FPU chips and microcontroller support software.


See the FAQ page for general information about floating point, and the uM-FPU V3 floating point coprocessor.

uM-FPU V3 - Known Problems

V3.0.3: When Debug Monitor is disabled, the TRACESTR instruction should not be used

If the debug monitor is disabled (TSTIN = Low at Reset), the TSTOUT pin is configured as an activity monitor. In this mode, there is a problem with the TRACESTR instruction. The TRACESTR opcode is being ignored, but the bytes of the string following the opcode are being executed as if they were instructions. For V3.0.3 and eariler, the TRACESTR instruction should not be used if the debug monitor is disabled.

uM-FPU V2 - Known Problems

uM-FPU V2 can hang after Reset if mode bits set.

If the Break on Reset or Trace on Reset mode bits have been set in the parameter byte, but the chip is wired with TSTIN low (debug monitor disabled), then the uM-FPU will hang after Reset. The mode bits can only be changed when TSTIN is high, so before wiring a circuit with TSTIN low (debug monitor disabled), make sure the Break on Reset and Trace on Reset mode bits are both clear.

When the FTOA instruction is used for unformatted output, the 8th digit of precision is sometimes not displayed properly.

The FTOA instruction is sometimes not accurate in the 8th digit of precision, but the internal value in the uM-FPU register is correct. For example, the internal value for pi is $40490FDB. The FTOA instruction returns the string "3.1415925" but the internal value is actually "3.1415927". Normally this is not a significant issue since the internal value used in calculations is correct. Only the string returned by FTOA is affected, and only in the 8th digit of precision.

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