Emerson MVME147 manual Open Packet

Open Packet

Even Byte \

Odd Byte \

	FC			B8		74	30
+$00			Controller LUN			Device LUN
+$02			Status Byte 0			Status Byte 1
+$04					Memory Address
+$06				+$08		Maximum	+$0A
						Number of Bytes
						to Transfer
+$0C			Maximum Number of Logical Bytes to Transfer
+$0E				+$10		0	0
0		0
+$12		0		0		0	0
+$14		Command Control				Function Code (7C = open)
+$16			Interrupt Level			Vector Number
+$18			Status Byte 2			Status Byte 3

This command reads the first blocks of a disk or tape up to the maximum number of bytes or the maximum number of blocks, whichever comes first.

If the requested number of blocks and the number of bytes match, the returned status is $00 (good).

If the requested number of blocks result in a transfer of more bytes than requested, the excess data is discarded and the returned status is $00 (good).

If the requested number of blocks result in a transfer of less bytes than requested, the returned status is $10 (byte count error).

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