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sys/dev/ppbus/lpt.c
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* Comments from Rod's probe: | * Comments from Rod's probe: | ||||
* Logic: | * Logic: | ||||
* 1) You should be able to write to and read back the same value | * 1) You should be able to write to and read back the same value | ||||
* to the data port. Do an alternating zeros, alternating ones, | * to the data port. Do an alternating zeros, alternating ones, | ||||
* walking zero, and walking one test to check for stuck bits. | * walking zero, and walking one test to check for stuck bits. | ||||
* | * | ||||
* 2) You should be able to write to and read back the same value | * 2) You should be able to write to and read back the same value | ||||
* to the control port lower 5 bits, the upper 3 bits are reserved | * to the control port lower 5 bits, the upper 3 bits are reserved | ||||
* per the IBM PC technical reference manauls and different boards | * per the IBM PC technical reference manuals and different boards | ||||
* do different things with them. Do an alternating zeros, alternating | * do different things with them. Do an alternating zeros, alternating | ||||
* ones, walking zero, and walking one test to check for stuck bits. | * ones, walking zero, and walking one test to check for stuck bits. | ||||
* | * | ||||
* Some printers drag the strobe line down when the are powered off | * Some printers drag the strobe line down when the are powered off | ||||
* so this bit has been masked out of the control port test. | * so this bit has been masked out of the control port test. | ||||
* | * | ||||
* XXX Some printers may not like a fast pulse on init or strobe, I | * XXX Some printers may not like a fast pulse on init or strobe, I | ||||
* don't know at this point, if that becomes a problem these bits | * don't know at this point, if that becomes a problem these bits | ||||
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