M2 Memory
MSC8113 Reference Manual, Rev. 0
Freescale Semiconductor
10-3
the current priority is upgraded when the SC140 core is frozen as an outcome of an open access
on the QBus.
Note:
If the SC140 core is frozen waiting to perform an instruction during the middle of a
cache line access, the prefetch access priority is not raised. If another core tries to
access the same bus with a high priority during the bus access sampling, the bus
arbitration will not grant access to the prefetch access. To avoid this unfair arbitration,
the user should enable all caches and prefetch simultaneously when running code from
external memory.
10.2 M2 Memory
M2 memory operates at the SC140 core frequency and is divided into 32 KB memory groups.
The M2 memory system includes the M2 memory and the MQBus. The memory has two main
ports:
MQBus port, 128-bit data read, 64-bit data write.
Local bus port, 64-bit read and write.
Each group is accessed through one of the main ports. A memory group is accessed from either
the MQBus or the local bus but not from both concurrently. When both ports access the same
memory group, the local bus port has a higher priority. When both ports access the same memory
group, the MQBus access stalls.
The first M2 memory read access by an SC140 core without a parked grant requires seven wait
states. If no other SC140 core requests the bus, the further consecutive accesses take six clock
cycles. If an SC140 core has a parked grant, the first access requires six wait states. An SC140
core read from M2 memory requires at least six (or eight) wait states. Since the ICache hit ratio is
high, these six (or eight) wait state accesses are rare. Because there are three SC140 cores in the
MSC8113, the MQBus may be occupied and one SC140 core access may require more than six
(or eight) wait states. However, an application that carefully considers memory allocation and
wisely uses the ICache significantly reduces the miss ratio of all three SC140 cores, reducing the
number of miss accesses to M2 memory.
10.3 Reservation Operation
The reservation atomic operation (bmtest instruction) is performed in two stages: a read of a
certain address content and a write of the modified content back to the original address. Between
these two accesses the atomic operation is defined as open. A write access of other SC140 cores
or external hosts to the same address causes the atomic operation to fail, and the SC140 core
atomic write operation to M2 memory is not performed.
The MQBus arbiter allows one such open atomic operation at a time. Other cores requesting an
atomic operation are serviced only after the current atomic operation is closed.
Summary of Contents for MSC8113
Page 1: ...MSC8113 Reference Manual Tri Core 16 Bit Digital Signal Processor MSC8113RM Rev 0 May 2008 ...
Page 20: ...MSC8113 Reference Manual Rev 0 xx Freescale Semiconductor Contents ...
Page 28: ...MSC8113 Reference Manual Rev 0 xxviii Freescale Semiconductor ...
Page 56: ...MSC8113 Reference Manual Rev 0 1 28 Freescale Semiconductor MSC8113 Overview ...
Page 76: ...MSC8113 Reference Manual Rev 0 2 20 Freescale Semiconductor SC140 Core Overview ...
Page 134: ...MSC8113 Reference Manual Rev 0 4 30 Freescale Semiconductor System Interface Unit SIU ...
Page 168: ...MSC8113 Reference Manual Rev 0 6 18 Freescale Semiconductor Boot Program ...
Page 180: ...MSC8113 Reference Manual Rev 0 7 12 Freescale Semiconductor Clocks ...
Page 260: ...MSC8113 Reference Manual Rev 0 8 80 Freescale Semiconductor Memory Map ...
Page 300: ...MSC8113 Reference Manual Rev 0 9 40 Freescale Semiconductor Extended Core ...
Page 304: ...MSC8113 Reference Manual Rev 0 10 4 Freescale Semiconductor MQBus and M2 Memory ...
Page 308: ...MSC8113 Reference Manual Rev 0 11 4 Freescale Semiconductor SQBus ...
Page 590: ...MSC8113 Reference Manual Rev 0 17 46 Freescale Semiconductor Interrupt Processing ...
Page 614: ...MSC8113 Reference Manual Rev 0 18 24 Freescale Semiconductor Debugging ...
Page 622: ...MSC8113 Reference Manual Rev 0 19 8 Freescale Semiconductor Internal Peripheral Bus IPBus ...
Page 724: ...MSC8113 Reference Manual Rev 0 21 32 Freescale Semiconductor UART ...
Page 920: ...MSC8113 Reference Manual Rev 0 25 150 Freescale Semiconductor Ethernet Controller ...
Page 1171: ...MSC8113 Reference Manual Rev 0 Freescale Semiconductor C 61 EF wait_rts P 01077FFC 9F rts 71 ...
Page 1172: ...MSC8113 Reference Manual Rev 0 C 62 Freescale Semiconductor MSC8113 Boot Code ...
Page 1202: ...MSC8113 Reference Manual Rev 0 Index 30 Freescale Semiconductor Index ...