Specifications

I/O Port 6-61
Table 6-32 INTR/IDENT Status Return Packet Description
Sparse Window Read Data Return Packet
The Sparse Window Read Data return packet is used by adapters on re-
mote buses that support I/O window space packets to return data re-
quested by a previous Sparse Window Read Command packet. The com-
mand field of the Sparse Window Read Data Return packet is E (hex).
Figure 6-30 shows the Sparse Window Read Data Return packet.
Figure 6-30 Sparse Window Read Data Return Packet
Table 6-33 gives the description of the Sparse Window Read Data Return
packet.
Field Description
Clock 1, <31:24>
Don’t Care. These bits, which normally form the TAG field, are don’t care,
since only one interrupt per IPL can be pending at a time and the corre-
sponding INTR/IDENT Status Return packet can be easily identified by
the IPL field.
Clock 1, <23:20>
Are always zero.
Clock 1, <19:16>
The IPL field is the interrupt priority level of the interrupt request. Bits
<19:16> correspond to IPL 17 to IPL 14, respectively. Only one IPL bit
should be set per packet. If more than one IPL bit is set, the I/O port con-
catenates the IPL bits with the TLCPUMASK and uses the result as the
data to be written to the TLIOINTR register in the CPUs. This could
cause interrupts to be simultaneously posted at different levels for each
IPL bit that was set. The vector that was in the packet will be returned
for each of the interrupts that are serviced by the CPUs. An
INTR/IDENT Status Return packet is returned across the Down Hose for
each interrupt serviced.
If no IPL bits are set in the INTR/IDENT packet, the I/O port still per-
forms a CSR write to the TLIOINTR register in the CPUs, but none of the
IPL bits is set, so no interrupt is posted. As a result, no INTR/IDENT
Status Return packet is returned across the Down Hose.
Clock 1, <15:0>
VECTOR<15:0> is the vector of the interrupt service routine.
Clock 2, <31:0>
Don’t care.
31 30 29 28 27 26 25 10 9 05
0 E VID Zero Count Zero
BXB-0788-94
30
1110
UPCTL
1*

2

3

* = clock cycle
6
xxxx
xxxx
Data Longword 0
Data Longword 1
UPD <31:0>