MPC555
/
MPC556
L-BUS TO U-BUS INTERFACE (L2U)
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
11-14
11.8.4 Region Base Address Registers (L2U_RBAx)
The region base address register defines the base address of a specific region pro-
tected by the data memory protection unit. There are four registers (x = 0...3), one for
each supported region.
x = Undefined
Table 11-7 L2U_MCR Bit Descriptions
Bit(s)
Name
Description
0
SP
SRAM Protection (SP) bit is used to protect the SRAM on the L-bus from U-bus accesses.
This bit can be set or cleared from the L-bus side. It can be set or cleared from the U-bus side
when factory test mode is enabled. When not in factory test mode, any attempt to set or clear the
SP bit from the U-bus side has no affect.
Once this bit is set, the L2U blocks all SRAM accesses initiated by the U-bus masters and the
access is terminated with a data error on the U-bus.
If L-bus show cycles are enabled, setting this bit will disable L-bus SRAM show cycles.
1:2
LSHOW
LSHOW bits are used to configure the show cycle mode for cycles accessing the L-bus slave e.g.
SRAM
00 = Disable show cycles
01 = Show address and data of all L-bus space write cycles
10 = Reserved
11 = Show address and data of all L-bus space read and write cycles
3:31
—
Reserved
L2U_RBAx
— L2U Region x Base Address Register
SPR 792 – 795
MSB
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
RBA
RESET:
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
LSB
31
RBA
RESERVED
RESET:
x
x
x
x
0
0
0
0
0
0
0
0
0
0
0
0
Table 11-8 L2U_RBAx Bit Descriptions
Bit(s)
Name
Description
0:19
RBA
Region base address. The RBA field provides the base address of the region. The region base
address should start on the block boundary for the corresponding block size attribute specified
in the region attribute register (L2U_RAx).
20:31
—
Reserved
F
re
e
sc
a
le
S
e
m
ic
o
n
d
u
c
to
r,
I
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
n
c
.
..