Typewriter User Manual

4- 20 MC68340 USER’S MANUAL MOTOROLA
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:
0000000000000000
CPU Space Only
MBAR 2 $0003FF02
1514131211109876543210
BA15 BA14 BA13 BA12 0 0 AS8 AS7 AS6 AS5 AS4 AS3 AS2 AS1 AS0 V
RESET
0000000000000000
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 address space (FC3–FC0 = 1xxx)
AS7—mask CPU Space address space (FC3–FC0 = 0111)
AS6—mask Supervisor Program address space (FC3–FC0 = 0110)
AS5—mask Supervisor Data address space (FC3–FC0 = 0101)
AS4—mask Reserved [Motorola] address space (FC3–FC0 = 0100)
AS3—mask Reserved [User] address space (FC3–FC0 = 0011)
AS2—mask User Program address space (FC3–FC0 = 0010)
AS1—mask User Data address space (FC3–FC0 = 0001)
AS0—mask Reserved [Motorola] address space (FC3–FC0 = 0000)
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.
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cale Semiconductor,
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