
110
Agere Systems Inc.
Data Sheet
May 2001
and Packet Payload Engine
Ambassador T8110 PCI-Based H.100/H.110 Switch
11 Minibridge
(continued)
11.2 Strobe Control Registers
The CS strobe inversion and RD-WR strobe inversion registers allow for programmable polarity of the MB_CS[7:0],
MB_RD, and MB_WR minibridge control strobes. Additionally, the polarity of the forwarded PCI_RST# signal (to
the GP(2) output) is selectable.
11.3 Minibridge Circuit Operation
The minibridge circuit accepts PCI memory read and memory write transactions and translates them into simple
asynchronous* control strobes for external devices hanging off the minibridge port.
The PCI address is passed straight through to the minibridge port, so MB_A[15:0] is always DWORD-aligned
(MB_A[1:0] = 00). Transactions are always 16-bit data, with the data on the PCI side always positioned at bits
PCI_AD[15:0]. Byte lane enables, PCI_CBEn[3:0], are ignored for minibridge transactions.
Refer to Section 4.1.6 on page 30 for more detail on the PCI side of the transactions. Refer to Figure 33 for the
access cycle descriptions of the minibridge side of the transactions.
* Asynchronous relative to the PCI clock. Strobes are generated relative to the internal chip clock in multiples of 65.536 MHz clock periods.
Table 85. Strobe Control Registers
DWORD
Address
(20 bits)
Register
Byte 3
Byte 2
Byte 1
Byte 0
0x00780
Reserved
Reserved
RD-WR strobe
inversion
CS strobe inversion
Byte Address
0x00780
Name
Bit(s) Mnemonic
7
Value
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0000 0
0
1
0
1
0
1
Function
CS Strobe Inversion
IC7SB
CS7 strobe is active-high (default).
CS7 strobe is active-low.
CS6 strobe is active-high (default).
CS6 strobe is active-low.
CS5 strobe is active-high (default).
CS5 strobe is active-low.
CS4 strobe is active-high (default).
CS4 strobe is active-low.
CS3 strobe is active-high (default).
CS3 strobe is active-low.
CS2 strobe is active-high (default).
CS2 strobe is active-low.
CS1 strobe is active-high (default).
CS1 strobe is active-low.
CS0 strobe is active-high (default).
CS0 strobe is active-low.
NOP (default).
Forward direct PCI_RST# (default).
Forward inverted PCI_RST#.
MB_RD strobe is active-high (default).
MB_RD strobe is active-low.
MB_WR strobe is active-high, (default).
MB_WR strobe is active-low.
6
IC6SB
5
IC5SB
4
IC4SB
3
IC3SB
2
IC2SB
1
IC1SB
0
IC0SB
0x00781
R/W Strobe Inversion
7:3
2
Reserved
IPRSB
1
IMRSB
0
IMWSB