Hi,
I'm designing a PC-side keyboard host controller clone (8042) for an embedded system. I'm facing a problem regarding the protocol-conformance tests. My intention is to desing test cases covering the behaviour of my clone upon the 'resend command' (0xF2) sent from the keyboard. I have examined several keyboard communication logs from two windows-based systems to see how other operating systems do that.
I deliberately put parity errors into the flow to squeeze out some resend responses. However I couldn't call forth any 'resend' command in the system-to-keyboard direction. (I could manage to get a few resend commands sent by the keyboard, in response to an erroneous command from the system, though.) I must not expect, that none of the OS implementations in the world use the resend command. (Otherwise why on earth did the docs below designate it?)
In my original PS/2 documentation (Keyboards 101- and 102 Key October 1990 IBM) there's a section about system commands and keyboard commands.
The following stands for resend as a system command: "Resend (Hex FE): The system sends this command when it detects an error in any transmission from the keyboard. It is sent only after a keyboard transmission and before the system allows the next keyboard output. When a Resend command is received, the keyboard sends the previous output again (unless the previous output was the Resend command, in which case the keyboard sends the last byte before the Resend command.)"
The following stands for resend as a keyboard command: "Resend (Hex FE): The keyboard issues a Resend command following receipt of an invalid input, or any input with incorrect parity."
I couldn't confirm the latter one by the systems I have tested. Can anyone confirm this?
In document Keyboard/Auxiliary device controller stands: "... 6. The auxiliary device checks for a positive-level stop bit after the
10th clock. If the 'data' line is inactive, the auxiliary device continues to clock until the 'data' line becomes active. Then it clocks the line-control bit and, at the next opportunity, sends a Resend command to the system"Can anyone confirm, that the keyboard really sends a resend in case of a false stop-bit?
Section Data output (from the keyboard's point of view): "...Following line contention, the system may or may not request the keyboard to resend the data."
Could you please tell me what sort of documentation it is? Could you please send it to me?
Do you know any system I could provoke to emit 'resend' commands in system-to-keyboard direction? Do you know any (PC) application meant for intensive PS/2 peripheral testing/debugging/error forcing?
Any help would be greatly appretiated.
Leslie