ez80f92 ZiLOG Semiconductor, ez80f92 Datasheet - Page 57

• Manufacturer Part Number: ez80f92
• Description: Ez80acclaim Flash Microcontrollers
• Manufacturer: ZiLOG Semiconductor

Table 13. Register Values for Memory Chip Select Example in Figure 6
PS015313-0508
Chip
Select
CS0
CS1
CS2
CS3
I/O Chip Select Operation
CSx_CTL[3]
CSx_EN
1
1
1
1
I/O Chip Selects can only be active when the CPU is performing I/O instructions. Because
the I/O space is separate from the memory space in the eZ80F92 device, there can never
be a conflict between I/O and memory addresses.
The eZ80F92 device supports a 16-bit I/O address. The I/O Chip Select logic decodes the
High byte of the I/O address, ADDR[15:8]. Because the upper byte of the address bus,
ADDR[23:16], is ignored, the I/O devices can always be accessed from within any mem-
ory mode (ADL or Z80
mode page is also always ignored.
Four I/O Chip Selects are available with the eZ80F92 device. To generate a particular I/O
Chip Select, the following conditions must be met:
•
•
•
•
•
•
The Chip Select is enabled by setting CSX_EN to 1
The Chip Select is configured for I/O by setting CSX_IO to 1
An I/O Chip Select address match occurs—ADDR[15:8] = CSx_LBR[7:0]
No higher-priority (lower-number) Chip Select meets the above conditions
The I/O address is not within the on-chip peripheral address range
On-chip peripheral registers assume priority for all addresses where:
0080h ≤ ADDR[15:0] ≤ 00FFh
An I/O instruction must be executing
CSx_CTL[4]
CSx_IO
0
0
0
0
CSx_LBR CSx_UBR Description
®
A0h
D0h
00h
00h
). The MBASE offset value used for setting the Z80 MEMORY
CFh
FFh
7Fh
9Fh
CS0 is enabled as a Memory Chip Select.
Valid addresses range from 000000h–
7FFFFFh.
CS1 is enabled as a Memory Chip Select.
Valid addresses range from 800000h–
9FFFFFh.
CS2 is enabled as a Memory Chip Select.
Valid addresses range from A00000h–
CFFFFFh.
CS3 is enabled as a Memory Chip Select.
Valid addresses range from D00000h–
FFFFFFh.
Chip Selects and Wait States
Product Specification
eZ80F92/eZ80F93
0080h
–
00FFh
.
50