MPC555
/
MPC556
L-BUS TO U-BUS INTERFACE (L2U)
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
11-12
1. L-bus slave includes all address in the L-bus address space.
2. L2U indicates L2U registers.
3. U-bus/E-bus refers to all destinations through the L2U interface.
4. There will be a 1-clock turnaround because the L-bus retry information is not available in time to negate the L-
bus arbitration.
Note: X indicates don’t care conditions.
11.8 L2U Programming Model
The L2U control registers control the L2U bus interface and the DMPU. They are ac-
cessible via the MPC555 / MPC556
mtspr
and
mfspr
instructions. They are also ac-
cessible by an external master when EMCR[CONT] bit is cleared. L2U control
registers are accessible from both the L-bus side and the U-bus side in one clock cy-
cle. As with all SPRs, L2U registers are accessible in supervisor mode only.
Any unimplemented bits in L2U registers return 0’s on a read, and the writes to those
register bits are ignored.
shows L2U registers along with their SPR numbers and hexadecimal
addresses which are used to access L2U registers during a peripheral mode access.
.
Table 11-4 L2U Show Cycle Support Chart
Case
Destination
LB AACK
LB ABORT
Comments
1
L-bus Slave
1
No
X
Not show cycled
[Cycle will be retried one clock later]
4
2
L2U
2
X
X
Not show cycled
3
U-bus/E-bus
3
X
X
Not show cycled
4
L-bus slave
Yes
No
Show cycled
5
L-bus slave
Yes
Yes
Not show cycled
[L-bus will be released next clock]
Table 11-5 L2U (PPC) Register Decode
Name
SPR #
SPR5:9
SPR0:4
Address for
External Master
Access
Access
Description
L2U_MCR
568
10001
11000
0x0000_3110
SUPR
L2U Module Configuration Register
L2U_RBA0
792
11000
11000
0x0000_3180
SUPR
Region Base Address Register 0
L2U_RBA1
793
11000
11001
0x0000_3380
SUPR
Region Base Address Register 1
L2U_RBA2
794
11000
11010
0x0000_3580
SUPR
Region Base Address Register 2
L2U_RBA3
795
11000
11011
0x0000_3780
SUPR
Region Base Address Register 3
L2U_RA0
824
11001
11000
0x0000_3190
SUPR
Region Attribute Register 0
L2U_RA1
825
11001
11001
0x0000_3390
SUPR
Region Attribute Register 1
L2U_RA2
826
11001
11010
0x0000_3590
SUPR
Region Attribute Register 2
L2U_RA3
827
11001
11011
0x0000_3790
SUPR
Region Attribute Register 3
L2U_GRA
536
10000
11000
0x0000_3100
SUPR
Global Region Attribute
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Freescale Semiconductor, Inc.
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