66 www.xilinx.com PowerPC™ 405 Processor Block Reference Guide
1-800-255-7778 UG018 (v2.0) August 20, 2004
Chapter 2: Input/Output Interfaces
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ISPLB 2:1 Core-to-PLB Line Fetch

The timing diagram in Figure2-12 shows an eight-word line fetch in a system with a PLB

clock that runs at one half the frequency of the PowerPC 405 clock.

The line read (rl1) is requested by the ICU in PLB cycle 2, which corresponds to PowerPC

405 cycle 3. The BIU responds in the same cycle. Instructions are sent from the BIU to the

ICU fill buffer in PLB cycles 3 through 6 (PowerPC 405 cycles 5 through 12). After all

instructions associated with this line are read, the line is transferred by the ICU from the fill

buffer to the instruction cache (not shown).

Figure 2-11: ISPLB Pipelined Non-Cacheable Sequential Fetch

Cycle 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20PLBCLK an d CPMC40 5CLK
UG018_16_101701
PPC405 Outputs:
C405PLBICUREQUESTC405PLBICUABUS[0:29]adr1 adr2byp2byp1prefetch2miss1ICUrl2rl1rl2rl1
PLB/BIU Outputs:
PLBC405ICUADDRACKPLBC405ICURDDBUS[0:63]PLBC405ICURDWDADDR[1:3]PLBC405ICURDDACK
rl167 rl101 rl123 rl145 rl201 rl223 rl245 rl267
d167 d101 d123 d145 d201 d223 d245 d26702466024PLBC405ICUBUSY

Figure 2-12: ISPLB 2 :1 Core-to-PLB Line Fetch

Cycle 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
CPMC40 5CLK
UG018_18_101701
PPC405 Outputs:
C405PLBICUREQUEST
C405PLBICUABUS[0:29] adr1
rl1rl1
PLB/BIU Outputs:
PLBC405ICUADDRACK
PLBC405ICURDDBUS[0:63]
PLBC405ICURDWDADDR[1:3]
PLBC405ICURDDACK rl101 rl123 rl145 rl167
d101 d123 d145 d167
0246miss1
ICU
PLBCLK
PLBC405ICUBUSY