Chapter 3 - MACSI Host Interface

Fetch offboard (FOB)

Setting this bit makes the Command Queue entry an offboard entry. Please see the following section for details.

Fetch offboard in progress (FIP)

This bit is used internally by the controller. It’s value should not be used by the host driver.

IOPB Address

This field contains a pointer to the IOPB for the command being issued, and is specified as an offset, in bytes, from the start of Short I/O space. The space occupied by the IOPB will be available for re-use as soon as the controller clears the Go bit, indicating that the command has been received.

Command Tag

This field is returned unchanged to the host upon completion of the command, and may be used to uniquely identify the returned command. Typically, the host driver would place a pointer to a control structure associated with the command in this field. The controller does not use the value in this field in any way.

Work Queue Number

This field is not currently used, though the value entered will be returned to the host.

Offboard Command Queue Entry

The following fields are defined for an offboard Command Queue entry.

Table 3-7. Offboard Command Queue Entry

Offboard Command Queue Entry

Offst

15

14

 

13

12

11

10

 

9

 

8

 

7

 

6

5

4

3

2

1

0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0x00

 

 

 

 

 

 

Queue Entry Control Register

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0x01

 

 

 

 

 

 

Dma Transfer Control Word

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0x02

 

 

 

 

 

 

 

Host Address (MSW)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0x03

 

 

 

 

 

 

 

Host Address (LSW)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0x04

 

 

Offboard Transfer Length

 

 

 

 

 

 

Work Queue Number

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0x05

 

 

 

 

 

 

 

 

 

Reserved

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Queue Entry Control Register (QECR)

The QECR field in the offboard entry is identical to the onboard version, except that the Fetch Offboard bit is set.

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