Emerson MVME147 manual DISK and TAPE

Read/Write Packet

space-to-end-of-recorded-media, or write command. To read, the controller must be at BOT or following a space-blocks, space-filemarks, or read command.

The command control field gives the user the ability to read forward or reverse (if supported by drive) and the ability to suppress illegal length indication (if supported by drive).

DISK and TAPE.

For scatter/gather operation, a non-zero value in the scatter/gather count indicates the memory and scatter/gather address field is the address of the scatter/gather table. The number of sectors field must be filled in and is also used to calculate the total byte count.

The details of a read/write packet are shown below.

New Packet

Even Byte \

Odd Byte \

	FC		B8		74		30
+$00		Controller LUN				Device LUN
+$02		Status Byte 0				Status Byte 1 (Note 1)
+$04			Memory Address (MSW) (Note 2)
+$06			Memory Address (LSW) (Note 2)
+$08				Sector Number (MSW)
+$0A				Sector Number (LSW)
+$0C			Number of Sectors to Transfer (MSW)
+$0E			Number of Sectors to Transfer (LSW)
+$10				Scatter/Gather Count
+$12		0		0		0		0
+$14		Command Control				Function Code (70, 74)
+$16		Interrupt Level				Vector Number
+$18		Status Byte 2				Status Byte 3 (Note 1)

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