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Memory Controller
MOTOROLA
MPC801 USER’S MANUAL
15-59
15
To connect to external memory devices that require address multiplexing, the MPC801 can
use the GPL5A and GPL5B signals to control external multiplexing logic. The GPL5
logic value is changed if you specify when any of the user-programmable machines in the
memory controller control the slave access. The GPL5
bit in the corresponding option register in the first clock cycle of the memory device access.
In the following cycles, the value is determined by the G5T4 and G5T3 bits in the user-
programmable machine’s RAM. If UPMB controls the slave access, the GL5A bit of the
option register indicates that the value of GL5, G5T4 and G5T3 in the UPMB controls the
logical value of the GPL5A signal. GL5S is only considered for read or write accesses to
memory and not for patterns initiated by the user-programmable machine as a result of an
internal periodic timer request or software request.
x
signal
x
signal reflects the value of the GL5S
Table 15-11. GPL5 Signal Behavior
MACHINE
CONTROLLING
MEMORY
ACCESS
MEMORY
ACCESS
CLOCK
CYCLE
G5LA
G5LS
G5T4
G5T3
GPL5
x
GPCM
x
x
x
x
x
GPL5A and GPL5B do not change their value.
UPMA
First
x
0
x
x
GPL5A is driven low at the falling edge of GCLK1.
1
GPL5A is driven high at the falling edge of GCLK1.
Second, Third...
x
x
0
x
GPL5A is driven low at the falling edge of GCLK2 in the
current UPM cycle.
1
x
GPL5A is driven high at the falling edge of GCLK2 in the
current UPM cycle.
x
0
GPL5A is driven low at the falling edge of GCLK1 in the
current UPM cycle.
x
1
GPL5A is driven high at the falling edge of GCLK1 in the
current UPM cycle.
UPMB
First
0
0
x
x
GPL5B is driven low at the falling edge of GCLK1.
1
GPL5B is driven high at the falling edge of GCLK1.
1
0
x
x
GPL5A is driven low at the falling edge of GCLK1.
1
GPL5A is driven high at the falling edge of GCLK1.
Second, Third...
0
0
0
x
GPL5B is driven low at the falling edge of GCLK2 in the
current UPM cycle.
1
x
GPL5B is driven high at the falling edge of GCLK2 in the
current UPM cycle.
x
0
GPL5B is driven low at the falling edge of GCLK1 in the
current UPM cycle.
x
1
GPL5B is driven high at the falling edge of GCLK1 in the
current UPM cycle.