MC68HC08AZ16 Datasheet, PDF (424/527 Pages) Motorola, Inc – HCMOS Microcontroller Unit

External Bus
Interface (EBI)
Module
Features
Appendix A: Related Devices
MC68HC08AZ0
This section describes the External Bus Interface Module (EBI)
specification for the MC68HC08AZ0 MCU. This module handles the
transfer of information between the MCU and the external address
space. The external bus provides up to 16 address lines, 8 data lines, 2
chip-selects and 3 control signals to the external devices.
• Up to 64K byte of Address Space.
• Low Noise or High Performance Modes of operation.
• 2 Pre-determined Chip-Select Lines (CS1 and CS0).
• Separate Read and Write Enable Signals
• 0,1,2 or 3 WAIT States for Slow Memory Access associated with
CS1
• Up to 7 WAIT States for Slow Device Access associated with CS0.
Figure 4 shows the structure of the EBI.
The EBI has two basic modes of operation; Low Noise or High
Performance. In Low Noise mode the Address and Data lines are only
driven out during external accesses to reduce RF emissions
In High Performance mode the EBI operates at its fastest. This mode of
operation requires the external address and data signals from the
MC68HC08AZ0 before they are stable.
The chip-select regions are controlled by software providing the user
with a choice of four combinations.The chip-selects have a control
register which allows the chip selects to be enabled, their polarity
selected and for the appropriate number of WAIT States to be defined
for CS0 and CS1.
11-appA
MOTOROLA
Appendix A: Related Devices
MC68HC08AZ32
423