Revision 1.02 – April 12, 2007
S5920 – PCI Product: Operation Registers
Data Book
This register provides empty/full visibility for each byte
within the mailboxes. The empty/full status for the
Add-On Incoming mailbox is displayed on bits 15 to 12
and the empty/full status for the Add-On Out-going
mailbox is presented on bits 31 to 28. A value of 1 sig-
nifies that a given mailbox has been written by one bus
interface but has not yet been read by the correspond-
ing destination interface. The Add-On bus incoming
mailbox is used to transfer data from the PCI bus to
the Add-On bus, and the Add-On outgoing mailbox is
used to transfer data from the Add-On bus to the PCI
bus. This register is also referred to as the PCI Mail-
box Empty/Full Status Register (MBEF).
ADD-ON MAILBOX EMPTY/FULL STATUS
REGISTER (AMBEF)
Mailbox Empty/Full Status
Register Name:
Add-On Address:
Power-up value:
Add-On Attribute:
Size:
34h
00000000h
Read Only
32 bits
Figure 32. Mailbox Empty/Full Status Register
31
28 27
16 15
12 11
0
0000
0000
Reserved
Reserved
Add-On Incoming Mailbox Status
(RO)
Add-On Outgoing Mailbox Status
(RO)
AMCC Confidential and Proprietary
DS1596
83
AMCC [ APPLIED MICRO CIRCUITS CORPORATION ]
