Emerson MVME147 manual Packet Return Status, Control Flags

PACKET RETURN STATUS

3

Packet Return Status

When packets are returned to the user, they contain two status words: one with an offset of $02 and the other with an offset of $18, as shown in the tables below, respectively. The first table details the status codes contained in the word at offset $02. Refer to the Interface Rules for the SCSI Firmware section in Chapter 5 for additional information. Also, refer to the command table returned fields.

Status word offset $02

1508 0700

Control Flags

Status Code (Refer to Table 3-1)

Bits 12-8 (reserved)

Bit 13 (RTE FLAG) (of interest only to the programmer)

1 = This return was not preceded by an interrupt and is the first return since command entry. In this case, no RTE is required.

0 = This return was preceded by an interrupt

and is not the first return, therefore, an RTE is required to continue proces- sing from where an interrupt occurred. Register A3 has a pointer to a register save area (D0-D7, A0-A6).

Bit 14 (ADDITIONAL STATUS) 1 = External status is valid.

0 = External status is not valid.