
Agere Systems Inc.
107
Data Sheet
May 2001
and Packet Payload Engine
Ambassador T8110 PCI-Based H.100/H.110 Switch
11 Minibridge
The T8110 provides for access to non-PCI devices from the PCI bus via the minibridge port.
Note:
If the T8110 is configured to interface to a microprocessor bus, the minibridge function is not applicable, and
the minibridge port pins are used for the microprocessor interface. Refer to Section 5 on page 38.
PCI access requests are converted to a simple interface to external devices hanging on the minibridge port. There
are eight chip select outputs, a read strobe, a write strobe, a 16-bit address and 16-bit data bus. Additionally, a for-
warded version of the PCI_RST# signal can be made available at the GP(2) output; refer to Section 6.1.1 on page
46 and Section 9.2.2.2 on page 101. PCI_AD[15:0], during the address phase, is DIRECTLY MAPPED as the
MB_A[15:0] address. Customers could possibly assume this, OR may assume that byte lane enables determine
the state of MB_A[1:0].
There is a direct mapping of the PCI address bits to the minibridge address bits. Users must be aware that
MB_A[1:0] of a minibridge transaction is a direct pass-thru from the PCI_AD[1:0] of the address phase, and for PCI
MEMORY transactions (which is the only type of transaction T8110 responds to), the value is always 00.
In addition, be aware that the minibridge only operates as 16-bit-only transfers, with the data positioned only on
bits [15:0] of PCI_AD during the data phase.
11.1 Wait-State Control Registers
11.1.1 Minibridge Wait-State Control Registers
The minibridge wait-state control registers allow for programmable assertion times for MB_CS[7:0], MB_RD, and
MB_WR control outputs. Resolution for the wait-state value increments is one 65.538 MHz clock period (15.25 ns);
refer to Figure 29 on page 104.
Table 83. Minibridge Wait-State Control Register Map
DWORD
Address
(20 bits)
Register
Byte 3
Byte 2
Byte 1
Byte 0
0x00700
0x00704
0x00710
0x00714
0x00720
0x00724
0x00730
0x00734
0x00740
0x00744
0x00750
0x00754
0x00760
0x00764
0x00770
0x00774
CS0 addr setup wait
CS0 addr hold wait
CS1 addr setup wait
CS1 addr hold wait
CS2 addr setup wait
CS2 addr hold wait
CS3 addr setup wait
CS3 addr hold wait
CS4 addr setup wait
CS4 addr hold wait
CS5 addr setup wait
CS5 addr hold wait
CS6 addr setup wait
CS6 addr hold wait
CS7 addr setup wait
CS7 addr hold wait
CS0 read hold wait
CS0 write hold wait
CS1 read hold wait
CS1 write hold wait
CS2 read hold wait
CS2 write hold wait
CS3 read hold wait
CS3 write hold wait
CS4 read hold wait
CS4 write hold wait
CS5 read hold wait
CS5 write hold wait
CS6 read hold wait
CS6 write hold wait
CS7 read hold wait
CS7 write hold wait
CS0 read width wait
CS0 write width wait
CS1 read width wait
CS1 write width wait
CS2 read width wait
CS2 write width wait
CS3 read width wait
CS3 write width wait
CS4 read width wait
CS4 write width wait
CS5 read width wait
CS5 write width wait
CS6 read width wait
CS6 write width wait
CS7 read width wait
CS7 write width wait
CS0 read setup wait
CS0 write setup wait
CS1 read setup wait
CS1 write setup wait
CS2 read setup wait
CS2 write setup wait
CS3 read setup wait
CS3 write setup wait
CS4 read setup wait
CS4 write setup wait
CS5 read setup wait
CS5 write setup wait
CS6 read setup wait
CS6 write setup wait
CS7 read setup wait
CS7 write setup wait