
Applied Micro Circuits Corporation
6195 Lusk Blvd., San Diego, CA 92121 (619) 450-9333
10-3
PCI CONTROLLER
S5933
DEVICE SPECIFICATION
S5933
PCI CONTROLLER
DEVICE SPECIFICATION
10.0 MAILBOX OVERVIEW
The S5933 has eight 32-bit mailbox registers. The mail-
boxes are useful for passing command and status infor-
mation between the Add-On and the PCI bus. The PCI
interface has four incoming mailboxes (Add-On to PCI)
and four outgoing mailboxes (PCI to Add-On). The Add-
On interface has four incoming mailboxes (PCI to Add-
On) and four outgoing mailboxes (Add-On to PCI). The
PCI incoming and Add-On outgoing mailboxes are the
same, internally. The Add-On incoming and PCI outgo-
ing mailboxes are also the same, internally.
The mailbox status may be monitored in two ways.
The PCI and Add-On interfaces each have a mailbox
status register to indicate the empty/full status of bytes
within the mailboxes. The mailboxes may also be con-
figured to generate interrupts to the PCI and/or Add-
On interface. One outgoing and one incoming mailbox
on each interface can be configured to generate inter-
rupts.
10.1 FUNCTIONAL DESCRIPTION
Figure 10-1 shows a block diagram of the PCI to
Add-On mailbox registers. Add-On incoming mailbox
read accesses pass through an output interlock latch.
This prevents a PCI bus write to a PCI outgoing mail-
box from corrupting data being read by the Add-On.
Figure 10-2 shows a block diagram of the Add-On to
PCI mailbox registers. PCI incoming mailbox reads
also pass through an interlocking mechanism. This
prevents an Add-On write to an outgoing mailbox
from corrupting data being read by the PCI bus. The
following sections describe the mailbox flag function-
ality and the mailbox interrupt capabilities.
MAILBOX
REGISTER
ADD-ON
BUS
"INCOMING
MAILBOX"
SELECT
OUTPUT
INTERLOCK
LATCH
OUTPUT
DRIVER
ADD-ON
BUS
MAILBOX
FULL
S
Q
D
"O"
LOAD ENABLE
READ ENABLE
EN
ADD-ON
RD#
SELECT#
EMPTY/FULL FF
Q
D
Q
D
PCI BUS
"OUTGOING MAILBOX"
SELECTED READ ENABLE
PCI
BUS
INTERFACE
ADD-ON
INTERFACE
"INCOMING MAILBOX"
Figure 10-1. Block Diagram - PCI to Add-On Mailbox Register
Figure 10-2. Block Diagram - Add-On to PCI Mailbox Register
MAILBOX
REGISTER
PCI
"INCOMING
MAILBOX"
SELECT
OUTPUT
INTERLOCK
LATCH
ADD-ON
BUS
"OUTGOING
MAILBOX"
WR#
SELECT#
PCI BUS
"INCOMING MAILBOX"
REGISTER
DECODE OF
ADR[6:2]
BE[3:0]#
MAILBOX
FULL
"O"
PCI READ PULSE
EMPTY/FULL FF
ADD-ON WRITE PULSE
SELECTED
READ PULSE
EN
Q
S
D
QD
PCI
BUS
INTERFACE
ADD-ON
INTERFACE