SCD1284 datasheet(91/176 Pages) INTEL

91 / 176 page

IEEE 1284-Compatible Parallel Interface Controller — CD1284

Datasheet

Internal firmware uses this operation to flag completion of the reset procedure. After the reset

is issued, the GFRCR is one of the first registers cleared and it is the last one set before normal

runtime code execution begins. The initialization routine must wait for this register to become

non-zero before it begins any other programming of CD1284 registers. If the CPU is

sufficiently fast, it could begin testing the GFRCR before the MPU clears it. The assumption

could be made that the CD1284 has completed internal initialization when, in fact, it has not

even started. To avoid this error, the CPU should look for the GFRCR to change to ‘0.’ It

should then look to the current revision code. Alternatively, the CPU can clear the GFRCR just

prior to issuing the global reset command and then poll for the correct revision code. This is

useful in slow systems that cannot guarantee that the CPU can check the register after it is

cleared or before it is loaded with the revision code.

This procedure is also used as part of a diagnostic test suite. The device completes internal

initialization within 500

µsec. A timer (software or hardware) detects when the operation is not

completed within that time and cues if the device is functional.

SCD1284 Datasheet(PDF) 91 Page - Intel Corporation