All Arcom circuit boards are inspected, built, tested and adjusted with great care before despatch, and your SFDC board will have been thoroughly checked to see that it reads and writes disks reliably. If you have problems therefore, please read the following guide before attempting to adjust the presets on the board.
PROBLEM | POSSIBLE CAUSES | SOLUTION |
Both drive LEDs come on as soon as power is applied | Cable between drive and SFDC is reversed. | Check connections. Check any disk in the drive it may be corrupted. |
The drive motor does not turn, or the drive light does not come on. | No power supplied to drive. | Check supply power. |
Incorrect drive jumpering. | Do the number the drive is jumpered for and the number being accessed correspond? | |
Bad connections to the SFDC board | Check the continuity of the inter-connecting cable. | |
The SFDC 'hangs' on all accesses. | Wrong address used. | Check that the address used corresponds with the the
address jumpers on the SFDC board. |
No system clock getting through. | Is pin 24 of the FDC i.e. receiving a clock pulse? (If not, check that your processor is supplying SYSCLK to the bus.) |
|
The SFDC 'hangs' only on Type II or Type III commands (see Appendix D for an explanation of these.) | No index pulse is reaching the FDC. | Check FDC pin 35. If it is not pulsing regularly then check the connector. |
No ready signal is being received. | Check FDC pin 32. If it does not go high a short time after the command then check the connector. | |
Although the drives start up, and accesses appear to be happening correctly, no valid data are acquired. | No serial data is reaching the FDC. | Check FDC pin 27, with the drive motor running. If it is not toggling fast then check the connector. |
The wrong density or drive-type has been selected. | Check that the bits being sent to the port are correct. | |
Data acquired, but not reliably. | The processor is not removing bytes from the FDC fast enough. | Check that the total access cycle time for your read operation is within the time given in Appendix D, including wait states. |
Electrical or magnetic interference is affecting the drive head or circuits. | If accessing inner tracks increases the error rate,
interference is the problem. Try screening the drive better or moving it away from possible sources of interference. |
|
The disk controller IC is operating at a temperature considerably different from that at which it was set up. | Wait to see if the error rate decreases once the board has warmed up. |
Equipment required:
Should you decide that your board is not functioning correctly due to maladjustment of the presets, follow the instructions below to set it up correctly. After this procedure the board will be set up to be able to read and write in all formats correctly.
Reset the board and select 8 inch single density made using the port.
If you have just switched on, allow at least 10 minutes for
the disk controller chip to reach normal operating temperature.
Make LK5. This connects pin 22 of the FDC chip to ground.
Measure the Read Pulse Width on pin 29 of the FDC.
Adjust VR2 until the width is 500ns.
Measure the VCO frequency on pin 16 of the FDC.
Adjust TC1 with a non-metallic tuning tool until the frequency is
250 KHz.
Measure the Write Precompensation Width on pin 31 of the FDC.
Adjust VR1 until the width is that required by your disk drives.
(If you are unsure about this, 80ns works for most 3.5 inch, 5.25 inch and 8 inch drives, and this adjustment is unnecessary anyway for drives with less than 43 tracks.
REMOVE LK5 for normal operation.