Revision 1.02 – April 12, 2007
S5920 – PCI Product: Operation Registers
Data Book
Table 45. Mailbox Empty/Full Status Register
Bit
Description
31:28
Add-On Outgoing Mailbox Status. This field indicates which byte of the outgoing mailbox register has been writ-
ten by the Add-On interface but has not yet been read by the PCI bus. Each bit location corresponds to a spe-
cific byte within the outgoing mailbox. A value of 1 for each bit signifies that the specified mailbox byte is full, and
a value of 0 signifies empty. The mapping of these status bits to bytes within the mailbox is as follows:
Bit 31 = Outgoing mailbox byte 3
Bit 30 = Outgoing mailbox byte 2
Bit 29 = Outgoing mailbox byte 1
Bit 28 = Outgoing mailbox byte 0
15:12
Add-On Incoming Mailbox Status. This field indicates which byte of the incoming mailbox register has been writ-
ten by the PCI bus interface but has not yet been read by the Add-On bus. Each bit location corresponds to a
specific byte within the incoming mailbox. A value of 1 for each bit signifies that the specified mailbox byte is full,
and a value of 0 signifies empty. The mapping of these status bits to bytes is as follows:
Bit 15 = Incoming mailbox byte 3
Bit 14 = Incoming mailbox byte 2
Bit 13 = Incoming mailbox byte 1
Bit 12 = Incoming mailbox byte 0
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