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ACT5260 数据表(PDF) 3 Page - Aeroflex Circuit Technology |
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ACT5260 数据表(HTML) 3 Page - Aeroflex Circuit Technology |
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3 / 10 page ![]() Aeroflex Circuit Technology SCD5260PC REV A 9/15/97 Plainview NY (516) 694-6700 3 Although the device has a 4XXX PC 179 pin PGA compatible footprint, it is not a drop-in replacement since the RM5260 has a different clocking scheme. The RM5260 does not generate the system clocks the same as the R4400, R4600 and R4700. Instead, the system clock is an input, which is multiplied up to the pipeline rate. On the adapter, the Tclock and Rclock pins are floating; not connected to anything. SYNCout and IOout are connected to ground to commit possible unconnected CMOS inputs to a level. Depending on the system configuration, accommodating the clocking difference can be as simple as a few re-routing jumpers or generating divisors of the original MasterClock and the addition of some phase-skewing buffers to emulate the Rclock and Tclock system clocks. In addition, the boot time mode bit serial stream needs to be scrutinized before plugging in a RM5260 into an R4700 or R4400 socket. The R4700 is closest to the RM5260 whereas the R4400 is quite different. Figure 2 is an example of what had to be done to an Algorithmics P4000i (IDT79S460) Single Board Computer which was originally configured for an R4700 with a 50 MHz input clock (100 MHz pipeline) and a divide by 2 output clock (50 MHz bus rate). With three wire jumpers, the ACT5260PC-P10-POD was up and running with no changes to the boot and monitor PROM or any recompilation of application programs. In this case, the R4700's modebit stream happened to be compatible, where a board jumper used to change the output clocks (Tclock and Rclock) from divide by 2 to divide by 3 had the effect of changing the Pclock multiplier from 2 to 3, upping the pipeline rate up to 150 Mhz without changing the board oscillator. Application Considerations: R4700 ACT5260PC Oscillator 50MHz Oscillator 50MHz Figure 2 – Setup Example From To |
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