Motorola DragonBall MC68328 User Manual page 43

System Integration Module
31 30 29 28
AC23 AC22 AC21 AC20
15 14 13 12
AM23 AM22 AM21 AM20
Address: $(FF)FFF130, 134, 138, 13C, 140, 144, 148, 14C
Figure 2-12. Chip-Select Registers for Group C and D
Chip selects in group A and B (i.e. CSA0, CSA1, CSA2, CSA3, CSB0, CSB1, CSB2, CSB3)
decode address A23-A16 (minimum 64K of space). Chip selects in group C and D decode
address A23-A12 (minimum 4K of space).
ADDRESS COMPARE 23-16 (Group A, B)
This bit field is the address-compare field. A group address match and a match of address
bits 23-16 generate this chip-select. Notice some of the address bits overlap in the group
base address/mask registers and the chip-select register. This allows for a large group to
be selected and for chip-select to be finely decoded.
ADDRESS MASK 23-16
This field masks corresponding bits in the address-compare field. A ''1'' forces a true com-
parison (don't care) on the corresponding bit.
ADDRESS COMPARE 23-12 (Group C, D)
This bit field is the address-compare field. A group address match and a match of address
bits 23-12 generate this chip-select.
ADDRESS MASK 23-12
This field masks corresponding bits in the address compare field. A "1" forces a true com-
parison (don't care) on the corresponding bit.
BSW Bus Width
This bit sets the bus width for this chip-select area.
0 = 8-bit
1 = 16-bit
RO Read Only
This bit sets the chip-select to read only. Otherwise, read and write accesses are allowed.
Writes to read-only areas generate a bus error.
0 = Read/Write
1 = Read Only
2-18 MC68328 DRAGONBALL PROCESSOR USER'S MANUAL
27 26 25 24
ADDRESS COMPARE 23-12
AC19 AC18 AC17 AC16
11 10 9 8
ADDRESS MASK 23-12
AM19 AM18 AM17 AM16
23 22 21 20
AC15 AC14 AC13 AC12
7 6 5 4
AM15 AM14 AM13 AM12
19 18 17 16
UNUSED BSW
- - - -
3 2 1 0
RO WAIT
- - - -
Reset Value: $00010006
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