Single-chip microcomputer with read clock generating circuits disposed in close proximity to memory macros
View Patent ↗Flash ROMs operate at a speed slower than that of a CPU. In order to raise the operating speed of a single-chip microcomputer, therefore, interleaving is adopted and a plurality of flash ROMs are operated alternately to obtain an apparent operating speed equivalent to that of a CPU. Read clock generating circuits are placed in close proximity to clock input pins of respective ones of the flash ROMs and supply the flash ROMs with read clocks obtained by dividing down the frequency of a system clock. Delay ascribable to wiring is eliminated from the read clocks as a result.
1. A microcomputer in which a CPU, a plurality of memory macros, and an interleave controller are positioned on a chip, said interleave controller allowing for interleaving in which the plurality of memory macros are operated alternately based on whether memory addresses output by the CPU for memory accesses are odd or even, said microcomputer comprising:
a plurality of dedicated read clock generating circuits;
wherein each dedicated read clock generating circuit of the plurality of dedicated read clock generating circuits is separate and apart from said interleave controller;
wherein each dedicated read clock generating circuit of the plurality of dedicated read clock generating circuits is configured to generate a respective read clock signal by receiving and frequency-dividing a system clock signal;
wherein each dedicated read clock generating circuit of the plurality of dedicated read clock generating circuits is connected to receive the system clock signal from a corresponding clock signal path that does not come from said interleave controller;
wherein each dedicated read clock generating circuit of the plurality of dedicated read clock generating circuits is configured to supply the respective read clock signal over a corresponding wire to a corresponding memory macro of the plurality of memory macros; and
wherein each dedicated read clock generating circuit of the plurality of dedicated read clock generating circuits is disposed on the chip in close proximity to the corresponding memory macro of the plurality of memory macros.
2. The microcomputer according to claim 1 , wherein each dedicated read clock generating circuit of said plurality of dedicated read clock generating circuits is disposed physically closer to a corresponding clock input pin of the corresponding memory macro of said plurality of memory macros than to the interleave controller.
3. The microcomputer according to claim 1 , wherein the system clock signal is supplied to each of the plurality of dedicated read clock generating circuits and to the interleave controller and to the CPU by a clock tree extending over the chip.
4. The microcomputer according to claim 1 , wherein each of said plurality of dedicated read clock generating circuits has input signals including said system clock signal, an address signal for identifying odd and even addresses, a memory-macro chip select signal, and a reconstructed state signal for discriminating a reconstructed state of an address; and
wherein said plurality of dedicated read clock generating circuits are configured to generate said respective read clocks by frequency-dividing the system clock signal based on said address signal, said memory-macro chip select signal, and said reconstructed state signal.
5. The microcomputer according to claim 1 ,
wherein said interleave controller is disposed physically closer to said CPU than to each of the plurality of dedicated read clock generating circuits;
wherein said interleave controller is configured to reconstruct addresses corresponding to the plurality of memory macros based upon address data from said CPU and is configured to output the addresses as addresses for accessing respective ones of the plurality of memory macros; and
wherein said interleave controller is configured to output data, which has been read out of the plurality of memory macros, to said CPU as data signals.
6. The microcomputer according to claim 1 , wherein the plurality of memory macros are flash ROMs.
7. The microcomputer according to claim 1 , wherein each of the plurality of memory macros is one of a ROM and a RAM.
8. The microcomputer according to claim 2 , wherein the system clock signal is supplied to each of the plurality of dedicated read clock generating circuits and to the interleave controller and to the CPU by a clock tree extending over the chip.
9. The microcomputer according to claim 2 , wherein each of said plurality of dedicated read clock generating circuits has input signals including said system clock signal, an address signal for identifying odd and even addresses, a memory-macro chip select signal, and a reconstructed state signal for discriminating a reconstructed state of an address; and
wherein said plurality of dedicated read clock generating circuits are configured to generate said respective read clocks by frequency-dividing the system clock signal based on said address signal, said memory-macro chip select signal, and said reconstructed state signal.
10. The microcomputer according to claim 3 , wherein each of said plurality of dedicated read clock generating circuits has input signals including said system clock signal, an address signal for identifying odd and even addresses, a memory-macro chip select signal, and a reconstructed state signal for discriminating a reconstructed state of an address; and
wherein said plurality of dedicated read clock generating circuits are configured to generate said respective read clocks by frequency-dividing the system clock signal based on said address signal, said memory-macro chip select signal, and said reconstructed state signal.
11. The microcomputer according to claim 2 ,
wherein said interleave controller is disposed physically closer to said CPU than to each of the plurality of dedicated read clock generating circuits;
wherein said interleave controller is configured to reconstruct addresses corresponding to the plurality of memory macros based upon address data from said CPU and is configured to output the addresses as addresses for accessing respective ones of the plurality of memory macros; and
wherein said interleave controller is configured to output data, which has been read out of the plurality of memory macros, to said CPU as data signals.
12. The microcomputer according to claim 3 ,
wherein said interleave controller is disposed physically closer to said CPU than to each of the plurality of dedicated read clock generating circuits;
wherein said interleave controller is configured to reconstruct addresses corresponding to the plurality of memory macros based upon address data from said CPU and is configured to output the addresses as addresses for accessing respective ones of the plurality of memory macros; and
wherein said interleave controller is configured to output data, which has been read out of the plurality of memory macros, to said CPU as data signals.
13. The microcomputer according to claim 4 ,
wherein said interleave controller is disposed physically closer to said CPU than to each of the plurality of dedicated read clock generating circuits;
wherein said interleave controller is configured to reconstruct addresses corresponding to the plurality of memory macros based upon address data from said CPU and is configured to output the addresses as addresses for accessing respective ones of the plurality of memory macros; and
wherein said interleave controller is configured to output data, which has been read out of the plurality of memory macros, to said CPU as data signals.
14. The microcomputer according to claim 1 ,
wherein each dedicated read clock generating circuit of said plurality of dedicated read clock generating circuits is disposed in close proximity to the corresponding memory macro of said plurality of memory macros such that a wiring delay of the respective read clock signal ascribable to a length of the corresponding wire is substantially eliminated.
15. A microcomputer, comprising:
a CPU positioned on a chip and connected to receive a system clock signal supplied by a clock tree;
a plurality of memory macros positioned on the chip;
an interleave controller positioned on the chip and coupled between said CPU and said plurality of memory macros, said interleave controller connected to receive said system clock signal from said clock tree; and
a plurality of read clock generating circuits;
wherein each read clock generating circuit of said plurality of read clock generating circuits is separate and apart from said interleave controller;
wherein each read clock generating circuit of said plurality of read clock generating circuits is connected to receive said system clock signal from said clock tree over a corresponding clock signal path that does not come from said interleave controller;
wherein each read clock generating circuit of said plurality of read clock generating circuits is configured to generate a respective read clock signal by frequency-dividing said system clock signal;
wherein each read clock generating circuit of said plurality of read clock generating circuits is connected to supply the respective read clock signal over a corresponding wire to a corresponding memory macro of the plurality of memory macros; and
wherein each read clock generating circuit of said plurality of read clock generating circuits is positioned on said chip physically closer to the corresponding memory macro of said plurality of memory macros than to the interleave controller.
16. The microcomputer according to claim 15 ,
wherein each of said plurality of read clock generating circuits has input signals including said system clock signal, an address signal for identifying odd and even addresses, a memory-macro chip select signal, and a reconstructed state signal for discriminating a reconstructed state of an address; and
wherein each of said plurality of read clock generating circuits is configured to generate said respective read clock by frequency-dividing the system clock signal based on said address signal, said memory-macro chip select signal, and said reconstructed state signal.
17. The microcomputer according to claim 15 ,
wherein said interleave controller is disposed physically closer to said CPU than to each of the plurality of read clock generating circuits;
wherein said interleave controller is configured to reconstruct addresses corresponding to the plurality of memory macros based upon address data from said CPU and is configured to output the addresses as addresses for accessing respective ones of the plurality of memory macros; and
wherein said interleave controller is configured to output data, which has been read out of the plurality of memory macros, to said CPU as data signals.
18. The microcomputer according to claim 15 , wherein the plurality of memory macros are flash ROMs.
19. The microcomputer according to claim 15 , wherein each read clock generating circuit of said plurality of read clock generating circuits is positioned on said chip in a respective position so as to minimize a wiring delay of the respective read clock signal due to a length of the corresponding wire.
20. The microcomputer according to claim 1 , wherein each dedicated read clock generating circuit of said plurality of dedicated read clock generating circuits is disposed on the chip in close proximity to the corresponding memory macro of the plurality of memory macros so as to minimize a wiring delay of the respective read clock signal due to a length of the corresponding wire.