GT-64260A Design Guide
Doc. No. MV-S300165-00, Rev. A
CONFIDENTIAL
Copyright © 2002 Marvell
Page 26
Document Classification: Proprietary Information
May 21, 2002, Preliminary
The GT-64260A translates the CPU transactions as shown in
For example, the boot GT-64260A (ID=’11’) responds to a read transaction from address 0xFFF00100. This trans-
action is translated to a read from the boot device at offset 0x100. A write transaction to address 0x00000000 gets
a response from the GT-64260A configured as ID=’00’. This transaction is translated to a write to its internal regis-
ter offset at 0x000.
For more information on the multi-GT initialization sequence and system considerations see the following:
•
The GT-64260A datasheet’s "CPU Interface" section
•
AN-91 Multi-GT Mode in the GT-6426xx
Notes
•
When multi-GT is enabled at reset, the NoMatch counter is only applicable to the GT-64260A boot.
•
In multi-GT mode AACK* and TA* pins have different AC timings. For details, see the GT-64260A
datasheet’s "AC Timing" section and the GT-64260A Documentation Updates and Changes docu-
ment.
3.7
CPU Bus Multiple Masters
The PowerPC bus protocol supports separate arbitration on address and data busses. The arbitration must be
implemented to support multiple masters on the CPU bus. The "multiple masters" configuration is usually used in
a Symmetric Multiple Processing (SMP) system. For an SMP system to be fully functional, it requires additional
HW implementations.
3.7.1 PowerPC Bus Arbitration
The GT-64260A supports both external arbiter and internal arbiter configurations. The arbiter configuration is sam-
pled at reset on the AD8 pin (see the GT-64260A datasheet’s "Reset Configuration" section).
If the internal arbiter is enabled, the BR0* pin is used as the CPU bus request input and BG0* and DBG0* are
used as the CPU bus grant and data bus grant outputs. In this configuration, the arbiter bus requests are BR0*,
BR1*, and CPU interface internal request (for bus mastering or snooping). Arbiter outputs are BG0* and DBG0* to
one master, BG1* and DBG1* for second bus master, and internal bus grants and data bus grants for the internal
CPU interface. The arbiter works in a fixed round robin scheme.
shows the connection of two CPUs to the
internal 60x arbiter.
Table 6:
Multi-GT Mode Transaction Translation
AD[4]
Transaction Type
Transaction Decode
‘0’
READ
Read from internal register when A[20-31]
defining the specific register offset.
‘1’
READ
Read access from boot device (BootCS*).
‘x’ (don’t care)
WRITE
Write to internal register when A[20-31] defin-
ing the specific register offset.