SEEK DIFFERENCES BETWEEN 2310 AND RK-05
The RK-05 seek interface sends a cylinder number and pulses a strobe signal, after which the drive either responds with an address accepted or an invalid address response signal. The timing for when the seek ends varies and another can be accepted is different from the 2310 as well.
The 2310 seek interface sends a direction, a step size and pulses a go signal. The step is one or two tracks and direction is forward or reverse. The drive reports an access-ready signal and a home signal. Home informs the controller that the arm is at track 0, the outer edge of the disk platter. Access ready goes off 5 ms after the access go pulse is sent and turns back on 10 ms after that, to reflect the 14.6 ms max time for arm movement.
Thus, the controller logic in the IBM 1130 will take a request for a relative movement of some number of tracks and convert it into multiple commands to the disk, using 1 and 2 track movements, until it is complete. If the arm reaches 0 and the command attempts to move in reverse, the arm remains at 0. Similarly, if the request for movement attempts to move the arm past 202, the last track, the arm remains at 202.
The RK-05 emulator turns on an LED indicator called 'on cylinder' as part of its seek emulation. I decided to use that inversely, as a seek in process indicator. To convert the action to human timescale, my logic turns on the indicator for a quarter second after each seek action. Since the 2310 moves in bursts of 1 or 2 tracks, it will go on steady on longer movements. A full seek across the cartridge can be 1.5 seconds long, but a one to two track movement is 15ms and the LED will be on for 250ms.
MODIFIED LOGIC AND SIMULATED SUCCESSFULLY
The logic is substantially different than for the RK-05. I simulated it with various conditions to verify both the behavior and the timing of every action. I was very pleased with the results and consider this part complete.
No comments:
Post a Comment