External Bus Interface
MPC885 PowerQUICC Family Reference Manual, Rev. 2
Freescale Semiconductor
13-35
13.4.9
Memory Reservation
The MPC885 memory reservation protocol supports multilevel bus structures. For each local bus,
reservations are handled by the local reservation logic. The protocol tries to optimize reservation
cancellation such that an MPC8xx core processor is notified of memory reservation loss on a remote bus
only when it has issued a STWCX cycle to that address. That is, the reservation loss indication comes as
part of the STWCX cycle, which avoids the need for fast memory reservation loss indication signals
between each remote bus and each MPC8xx master. The memory reservation protocol assumes the
following:
•
Each processor has no more than one reservation flag.
•
lwarx sets the reservation flag.
•
lwarx by the same processor clears the reservation flag related to a previous lwarx instruction and
again sets the reservation flag.
•
stwcx. by the same processor clears the reservation flag.
•
Store by the same processor does not clear the reservation flag.
•
Some other processor (or other mechanism) store to the same address as an existing reservation
clears the reservation flag.
•
If memory reservation is lost, it is guaranteed that stwcx. will not modify the memory.
13.4.9.1
Cancel Reservation (CR)
CR is a point-to-point signal. To use it, reservation logic must remember specifically which bus master
requested reservation for which address. If another master writes to the reserved address, the reservation
logic asserts CR only to the master that holds the associated reservation, thus clearing its flag.
The advantage of CR is that it preempts the stwcx. instruction if reservation is lost, thus eliminating
unnecessary traffic on the external bus.
Figure 13-27
shows the reservation protocol for a single-level (local) bus. It assumes that an external logic
on the bus handles the following:
•
Snoops accesses to all local bus slaves.
•
Holds one reservation for each local master capable of memory reservations.
•
Sets the reservation when that master issues a load and reserve request.
•
Clears the reservation when another master issues a store to the reservation address.
Содержание PowerQUICC MPC870
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Страница 118: ...MPC885 Overview MPC885 PowerQUICC Family Reference Manual Rev 2 1 20 Freescale Semiconductor ...
Страница 158: ...The MPC8xx Core MPC885 PowerQUICC Family Reference Manual Rev 2 3 18 Freescale Semiconductor ...
Страница 192: ...MPC885 Instruction Set MPC885 PowerQUICC Family Reference Manual Rev 2 5 22 Freescale Semiconductor ...
Страница 242: ...Instruction and Data Caches MPC885 PowerQUICC Family Reference Manual Rev 2 7 30 Freescale Semiconductor ...
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Страница 416: ...External Bus Interface MPC885 PowerQUICC Family Reference Manual Rev 2 13 42 Freescale Semiconductor ...
Страница 440: ...Clocks and Power Control MPC885 PowerQUICC Family Reference Manual Rev 2 14 24 Freescale Semiconductor ...
Страница 554: ...MPC885 PowerQUICC Family Reference Manual Rev 2 V 6 Freescale Semiconductor ...
Страница 606: ...SDMA Channels and IDMA Emulation MPC885 PowerQUICC Family Reference Manual Rev 2 19 20 Freescale Semiconductor ...
Страница 738: ...SCC Asynchronous HDLC Mode and IrDA MPC885 PowerQUICC Family Reference Manual Rev 2 25 16 Freescale Semiconductor ...
Страница 780: ...SCC Ethernet Mode MPC885 PowerQUICC Family Reference Manual Rev 2 27 24 Freescale Semiconductor ...
Страница 794: ...SCC Transparent Mode MPC885 PowerQUICC Family Reference Manual Rev 2 28 14 Freescale Semiconductor ...
Страница 848: ...Serial Peripheral Interface SPI MPC885 PowerQUICC Family Reference Manual Rev 2 30 18 Freescale Semiconductor ...
Страница 882: ...Universal Serial Bus USB MPC885 PowerQUICC Family Reference Manual Rev 2 31 34 Freescale Semiconductor ...
Страница 944: ...Parallel I O Ports MPC885 PowerQUICC Family Reference Manual Rev 2 34 26 Freescale Semiconductor ...
Страница 956: ...CPM Interrupt Controller MPC885 PowerQUICC Family Reference Manual Rev 2 35 12 Freescale Semiconductor ...
Страница 1004: ...Buffer Descriptors and Connection Tables MPC885 PowerQUICC Family Reference Manual Rev 2 37 30 Freescale Semiconductor ...
Страница 1022: ...ATM Parameter RAM MPC885 PowerQUICC Family Reference Manual Rev 2 38 18 Freescale Semiconductor ...
Страница 1068: ...ATM Pace Control MPC885 PowerQUICC Family Reference Manual Rev 2 40 22 Freescale Semiconductor ...
Страница 1090: ...UTOPIA Interface MPC885 PowerQUICC Family Reference Manual Rev 2 43 8 Freescale Semiconductor ...
Страница 1120: ...AAL2 Implementation MPC885 PowerQUICC Family Reference Manual Rev 2 44 30 Freescale Semiconductor ...
Страница 1162: ...Fast Ethernet Controller FEC MPC885 PowerQUICC Family Reference Manual Rev 2 45 40 Freescale Semiconductor ...
Страница 1172: ...SEC Lite Overview MPC885 PowerQUICC Family Reference Manual Rev 2 46 8 Freescale Semiconductor ...
Страница 1176: ...SEC Lite Address Map MPC885 PowerQUICC Family Reference Manual Rev 2 47 4 Freescale Semiconductor ...
Страница 1214: ...SEC Lite Execution Units MPC885 PowerQUICC Family Reference Manual Rev 2 48 38 Freescale Semiconductor ...
Страница 1312: ...Byte Ordering MPC885 PowerQUICC Family Reference Manual Rev 2 A 8 Freescale Semiconductor ...
Страница 1313: ...MPC885 PowerQUICC Family Reference Manual Rev 2 Freescale Semiconductor B 1 Appendix B Serial Communications Performance TBD ...
Страница 1314: ...Serial Communications Performance MPC885 PowerQUICC Family Reference Manual Rev 2 B 2 Freescale Semiconductor ...
Страница 1320: ...Register Quick Reference Guide MPC885 PowerQUICC Family Reference Manual Rev 2 C 6 Freescale Semiconductor ...
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Страница 1370: ...MPC880 MPC885 PowerQUICC Family Reference Manual Rev 2 E 4 Freescale Semiconductor ...
Страница 1384: ...Serial ATM Scrambling Reception and SI Programming MPC885 PowerQUICC Family Reference Manual Rev 2 H 6 Freescale Semiconductor ...
Страница 1386: ...Revision History MPC885 PowerQUICC Family Reference Manual Rev 2 I 2 Freescale Semiconductor ...