108 www.xilinx.com PowerPC™ 405 Processor Block Reference Guide
1-800-255-7778 UG018 (v2.0) August 20, 2004
Chapter 2: Input/Output Interfaces
R
DCR Interface 2:1 Clocking, Latched Acknowledge

The example in Figure 2-35 assumes the following:

xThe PowerPC 405 DCR interface is clocked at twice the frequency of the peripheral

containing the addressed DCR.

xThe acknowledge signal is latched and forwarded with the DCR bus as shown in

Figure 2-31, page 103.

xAfter the acknowledge signal is asserted, it is not deasserted until the appropriate

read-access or write-access request signal is deasserted.

Figure 2-34: DCR Interface 1:1 Clocking, Combinatorial Acknowledge

Cycle
CPMC405CLOCK (Virtex-II Pro)/
CPMDCRCLK (Virtex-4 FX)
DCR (FPGA) Clock
UG018_42_032504
DCRWRITE/DCRREAD
DCRABUS[0:9]
PPC405 Outputs:
DCRDBUSOUT[0:31]
DCRDBUSIN[0:31]
DCRACK
DCR Outputs:
data0 data1 data2
addr0 addr1 addr2
data0 data1 data2
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Note: Abbreviated signal names are used.

Figure 2-35: DCR Inter face 2:1 Clocking, Latched Acknowledge

Cycle
CPMC405CLOCK (Virtex-II Pro)/
CPMDCRCLK (Virtex-4 FX)
DCR (FPGA) Clock
UG018_43_042304
DCRWRITE/DCRREAD
DCRABUS[0:9]
PPC405 Outputs:
DCRDBUSOUT[0:31]
DCRDBUSIN[0:31]
DCRACK
DCR Outputs:
data0 data1
addr0 addr1
data0 data1
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Note: Abbreviated signal names are used.