MOTOROLA
Chapter 10. Memory Controller
10-63
Part III. The Hardware Interface
Additional control is available in 60x-compatible mode (60x bus only)ÑALEÑExternal
address latch enable (not a UPM-controlled signal).
Note that in this section, when a signal is named, the reference is to the 60x or local bus
signal, according to the bank being accessed.
The three user-programmable machines (UPMs) are ßexible interfaces that connect to a
wide range of memory devices. At the heart of each UPM is an internal-memory RAM
array that speciÞes the logical value driven on the external memory controller pins for a
given clock cycle. Each word in the RAM array provides bits that allow a memory access
to be controlled with a resolution of up to one quarter of the external bus clock period on
the byte-select and chip-select lines. Figure 10-55 shows the basic operation of each UPM.
The following events initiate a UPM cycle:
¥
Any internal or external device requests an external memory access to an address
space mapped to a chip-select serviced by the UPM
¥
A UPM refresh timer expires and requests a transaction, such as a DRAM refresh
¥
A transfer error or reset generates an exception request
Figure 10-55. User-Programmable Machine Block Diagram
The RAM array contains 64 32-bit RAM words. The signal timing generator loads the
RAM word from the RAM array to drive the general-purpose lines, byte-selects, and
chip-selects. If the UPM reads a RAM word with WAEN set, the external UPWAIT signal
is sampled and synchronized by the memory controller and the current request is frozen.
When a new access to external memory is requested by any device on the 60x or local bus,
the addresses of the transfer are compared to each one of the valid banks deÞned in the
memory controller. When an address match is found in one of the memory banks, BR
x
[MS]
selects the UPM to handle this memory access. M
x
MR[BS] assigns the UPM to the 60x or
the local bus.
RUN
command
UPM refresh
timer request
Array
Index
Generator
Internal/external
memory access request
Exception request
Index
Signals
Timing
Generator
Internal
Signals
Latch
Wait
Request
Logic
RAM Array
UPWAIT
WAEN Bit
Internal Controls
GPL
x
, BS_
x
, CS
x
Increment
Index
(LAST = 0)
Hold
(issued in software)
Summary of Contents for MPC8260 PowerQUICC II
Page 1: ...MPC8260UM D 4 1999 Rev 0 MPC8260 PowerQUICC II UserÕs Manual ª ª ...
Page 66: ...lxvi MPC8260 PowerQUICC II UserÕs Manual MOTOROLA ...
Page 88: ...1 18 MPC8260 PowerQUICC II UserÕs Manual MOTOROLA Part I Overview ...
Page 120: ...2 32 MPC8260 PowerQUICC II UserÕs Manual MOTOROLA Part I Overview ...
Page 138: ...Part II iv MPC8260 PowerQUICC II UserÕs Manual MOTOROLA Part II Configuration and Reset ...
Page 184: ...4 46 MPC8260 PowerQUICC II UserÕs Manual MOTOROLA Part II ConÞguration and Reset ...
Page 202: ...Part III vi MPC8260 PowerQUICC II UserÕs Manual MOTOROLA Part III The Hardware Interface ...
Page 266: ...8 34 MPC8260 PowerQUICC II UserÕs Manual MOTOROLA Part III The Hardware Interface ...
Page 382: ...10 106 MPC8260 PowerQUICC II UserÕs Manual MOTOROLA Part III The Hardware Interface ...
Page 392: ...11 10 MPC8260 PowerQUICC II UserÕs Manual MOTOROLA Part III The Hardware Interface ...
Page 430: ...Part IV viii MOTOROLA Part IV Communications Processor Module ...
Page 490: ...14 36 MPC8260 PowerQUICC II UserÕs Manual MOTOROLA Part IV Communications Processor Module ...
Page 524: ...17 10 MPC8260 PowerQUICC II UserÕs Manual MOTOROLA Part IV Communications Processor Module ...
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Page 980: ...A 4 MPC8260 PowerQUICC II UserÕs Manual MOTOROLA Appendixes ...
Page 1002: ...Index 22 MPC8260 PowerQUICC II UserÕs Manual MOTOROLA INDEX ...
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