TARGET Enable Custom Packet
This second "class" of custom packets is used to enable TARGET role service by the MVME147 SCSI firmware. All eight SCSI-defined logical units can be independently serviced through the firmware. Each logical unit needs to be enabled separately. In other words, a TARGET enable packet is sent for each logical unit that you want to service. The TARGET enable packet should not be deallocated even after TARGET is enabled and command is received (final return for TARGET enable). It is recommended that you use the same packet for TARGET enable and TARGET sequence. The last packet should be saved until the next TARGET command is received.
Packet description:
WORD $00: CONTROLLER LUN -- This is the target SCSI address of the MVME147. Because target firmware already knows the SCSI address this field is used to compare with the known target SCSI address. If the address does not match, an ID error is reported when the packet is received.
DEVICE LUN -- This number (0 through 7) specifies which TARGET logical unit is to be enabled. All eight may be enabled, but only one is enabled per TARGET enable call.
WORD $02: STATUS bytes 0 and 1 -- These status bytes are the codes returned to you by the firmware. (For code definitions, refer to Chapter 3.)
WORDS $04 and $06:
SCRIPT POINTER -- The script pointer is not used by the firmware for the TARGET enable call.
WORDS $08 and $0A:
COMMAND TABLE POINTER -- This is the pointer to the command table (384 bytes of RAM). Each TARGET logical unit needs one command table. No sharing of command tables is allowed among the enabled logical units. When a TARGET command is complete, this command table must not be deallocated because of future use. However, the command table area could be used by subsequent TARGET commands.
WORD $0E=$C000:
This code classifies the custom packet as a TARGET enable call to the firmware.
WORD $14: The code of $1C classifies the packet as a custom packet.
