Memory Controller
MPC885 PowerQUICC Family Reference Manual, Rev. 2
Freescale Semiconductor
15-45
15.6.4.5
Loop Control (LOOP)
The LOOP bit in the RAM word (bit 24) specifies the beginning and end of a set of UPM RAM words that
are to be repeated. The first time LOOP = 1, the memory controller recognizes it as a loop start word and
loads the memory loop counter with the corresponding contents of the loop field shown in
Table 15-17
.
The next RAM word for which LOOP = 1 is recognized as a loop end word. When it is reached, the loop
counter is decremented by one.
Continued loop execution depends on the loop counter. If the counter is not zero, the next RAM word
executed is the loop start word. Otherwise, the next RAM word executed is the one after the loop end word.
Loops can be executed sequentially but cannot be nested.
UPMB
First
0
0
x
x
GPL_B5 is driven low at the falling edge of GCLK1_50.
1
GPL_B5 is driven high at the falling edge of GCLK1_50.
1
0
x
x
GPL_A5 is driven low at the falling edge of GCLK1_50.
1
GPL_A5 is driven high at the falling edge of GCLK1_50.
Second, third...
0
x
0
x
GPL_B5 is driven low at the falling edge of GCLK2_50 in
the current UPM cycle.
1
x
GPL_B5 is driven high at the falling edge of GCLK2_50 in
the current UPM cycle.
x
0
GPL_B5 is driven low at the falling edge of GCLK1_50 in
the current UPM cycle.
x
1
GPL_B5 is driven high at the falling edge of GCLK1_50 in
the current UPM cycle.
1
x
0
x
GPL_A5 is driven low at the falling edge of GCLK2_50 in
the current UPM cycle.
1
x
GPL_A5 is driven high at the falling edge of GCLK2_50 in
the current UPM cycle.
x
0
GPL_A5 is driven low at the falling edge of GCLK1_50 in
the current UPM cycle.
x
1
GPL_A5 is driven high at the falling edge of GCLK1_50 in
the current UPM cycle.
Table 15-17. M
x
MR Loop Field Usage
Request Serviced
Loop Field
Read single-beat cycle
RLFx
Read burst cycle
RLFx
Write single-beat cycle
WLFx
Table 15-16. GPL_x5 Signal Behavior (continued)
Controlling Machine
OR
x RAM
Word
GPL_x5 Behavior at the Controlling Clock Edge
Memory
Access
Slave Access
Clock Cycle
G5LA
G5LS
G5T4
G5T3
Summary of Contents for PowerQUICC MPC870
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