EZ80L92MCU Datasheet, PDF (64/241 Pages) Zilog, Inc. – eZ80Acclaim Flash Microcontrollers

eZ80L92 MCU
Product Specification
49
Memory Chip Select Priority
A lower-numbered Chip Select is granted priority over a higher-numbered Chip Select.
For example, if the address space of Chip Select 0 overlaps the Chip Select 1 address
space, Chip Select 0 is active.
RESET States
On RESET, Chip Select 0 is active for all addresses, because its Lower Bound register
resets to 00h and its Upper Bound register resets to FFh. All of the other Chip Select
Lower and Upper Bound registers reset to 00h.
Memory Chip Select Example
The use of Memory Chip Selects is demonstrated in Figure 4. The associated control reg-
ister values indicated in Table 13. In this example, all 4 Chip Selects are enabled and con-
figured for memory addresses. Also, CS1 overlaps with CS0. Because CS0 is prioritized
higher than CS1, CS1 is not active for much of its defined address space.
CS3_UBR = FFh
CS3_LBR = D0h
CS2_UBR = CFh
CS2_LBR = A0h
CS1_UBR = 9Fh
CS0_UBR = 7Fh
CS3 Active
3 MB Address Space
CS2 Active
3 MB Address Space
CS1 Active
2 MB Address Space
Memory
Location
FFFFFFh
D00000h
CFFFFFh
A00000h
9FFFFFh
800000h
7FFFFFh
CS0 Active
8 MB Address Space
CS0_LBR = CS1_LBR = 00h
Figure 4. Memory Chip Select Example
000000h
PS013012-1004
PRELIMINARY
Chip Selects and Wait States