Operation procedure

This section explains how to get a control right and how to read/write data on P-PCI-LV. To have the control right means that the interface has a right to determine the direction of data transfer.

• get the control right.
  1. set 1 into RUNMOD in Mode register and then set 0 into PRV in Mode register for getting PRV.
  2. Read Status register.
  3. If PRV bit in Status register is set, another board already has the control right. Thus, this board sets 1 into PRV bit in Mode register for becoming non-PRV board.
  4. Check the direction of data transfer. For input, the DIR bit in Mode register should be 1 if another board has the control right. The bit should be 0 if this board has the control right. For output, the bit should be 0 if another board has the control right. The bit should be 1 if this board has the control right. Otherwise, the direction error occurs. You should check the direction and corrects it.

• Read/Write operation(as PCI bus master)
  1. Check the specified data size.
  2. Enables the forced-end interrupt and the normal-end interrupt.
  3. On the write operation, data in user's buffer should be copied into kernel buffer.
  4. Set the physical address of data buffer into Transfer address register of P-PCI-LV.
  5. Set the byte count to be transferred into Transfer count register of P-PCI-LV. The value subtracted by 1 should be written.
  6. Set this board in master mode(start DMA).
  7. Wait for an interrupt, forced-end, normal-end or timeout interrupt. If the timeout occurred, returns with error condition. Otherwise, go next step.
  8. Get actual length of data transferred, from RetLength register in P-PCI-LV. On the read operation, data should be copied into user's buffer.
  9. Return with the actual length.