Freescale Semiconductor, Inc.
4.3.1 Module Base Address Register (MBAR)
MBAR 1
$0003FF00
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
BA31
BA30
BA29
BA28
BA27
BA26
BA25
BA24
BA23
BA22
BA21
BA20
BA19
IBA18
BA17
BA16
RESET:
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
CPU Space Only
$0003FF02
MBAR 2
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
BA15
BA14
BA13
BA12
0
0
AS8
AS7
AS6
AS5
AS4
AS3
AS2
AS1
AS0
V
RESET
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
CPU Space Only
BA31–BA12—Base Address Bits 31–12
The base address field is the upper 20 bits of the MBAR that provides for block starting
locations in increments of 4-Kbytes.
Bits 11, 10—Reserved
AS8–AS0—Address Space Bits 8–0
The address space field allows particular address spaces to be masked, placing the 4K
module block into a particular address space(s). If an address space is masked, an
access to the register block location in that address space becomes an external access.
The module block is not accessed. The address space bits are as follows:
AS8—mask DMA Space
AS7—mask CPU Space
address space (FC3–FC0 = 1xxx)
address space (FC3–FC0 = 0111)
address space (FC3–FC0 = 0110)
address space (FC3–FC0 = 0101)
address space (FC3–FC0 = 0100)
address space (FC3–FC0 = 0011)
address space (FC3–FC0 = 0010)
address space (FC3–FC0 = 0001)
address space (FC3–FC0 = 0000)
AS6—mask Supervisor Program
AS5—mask Supervisor Data
AS4—mask Reserved [Motorola]
AS3—mask Reserved [User]
AS2—mask User Program
AS1—mask User Data
AS0—mask Reserved [Motorola]
For each address space bit:
1 = Mask this address space from the internal module selection. The bus cycle goes
external.
0 = Decode for the internal module block.
V—Valid Bit
This bit indicates when the contents of the MBAR are valid. The base address value is
not used; therefore, all internal module registers are not accessible until the V-bit is set.
1 = Contents are valid.
0 = Contents are not valid.
4- 20
MC68340 USER’S MANUAL
MOTOROLA
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