Specifications

6-54 I/O Port
Table 6-24 Mailbox Status Return Packet Description
DMA Read
The DMA Read packet is a request on the Up Hose from the I/O bus
adapter to the I/O port for a data read transaction on the TLSB bus.
The requested data for a DMA Read packet is returned on the Down Hose
with a DMA Read Data Return packet. Figure 6-25 shows the DMA Read
packet.
Figure 6-25 DMA Read Packet
Table 6-24 gives the description of the DMA Read packet.
Field Description
Clock 1 and 2,
<31:0>
The return data longword 0 and 1 fields, respectively. The return data
fields contain read data in response to Mailbox Command packets that
were reads. This data is Unpredictable when responding to Mailbox Com-
mand packets that were writes.
Clock 3, <31:2>
Device specific field <29:0>. The device specific field contains operation
completion status. The interpretation of this field is defined by the I/O bus
adapter module.
Clock 3, <1>
The Error bit. If an error was detected by the I/O adapter, the Error bit
will be set.
Clock 3, <0>
The Done bit. This bit is always set in a mailbox return packet.
Clock 4, <31:0>
Device specific field <61:30>. The device specific field contains operation
completion status. The interpretation of this field is defined by the I/O bus
adapter.
31 24 23 11 10 087
TAG<7:0> 0 LEN ADR <39:32>
BXB-0278-92
ADR <31:0>
30
0001
UPD <31:0>
UPCTL
xxxx
1*

2
* = hose cycle