SAF-C164SM Infineon Technologies, SAF-C164SM Datasheet - Page 176

• Manufacturer Part Number: SAF-C164SM
• Description: 16-Bit CMOS Microcontroller
• Manufacturer: Infineon Technologies

bus modes, the address is also required on PORT0. In this special case, the address on
PORT0 is delayed by one CPU clock cycle; this delays the complete (multiplexed) bus
cycle and extends the corresponding ALE signal (see
This extra time is required to allow the previously selected device (via demultiplexed bus)
to release the data bus, which would be available in a demultiplexed bus cycle.
Figure 9-4
Switching between external resources (such as different peripherals) may incur a
problem if the previously accessed resource needs some time to switch off its output
drivers (after a read) and the resource to be accessed next switches its output drivers on
very quickly. In systems running at higher frequencies, this may lead to a bus conflict (the
switch off delays are normally independent from the clock frequency).
In such a case, an additional waitstate can automatically be inserted when leaving a
certain address window, i.e. when the next cycle accesses a different window. This
waitstate is controlled in the same way as the waitstate when switching from
demultiplexed to multiplexed bus mode, see
BUSCON switch waitstates are enabled via bits BSWCx in the BUSCON registers. By
enabling the automatic BUSCON switch waitstate (BSWCx = ‘1’) there is no impact on
the system performance as long as the external bus cycles access the same address
window. Only if the following cycle accesses a different window is a waitstate inserted
between the last access to the previous window and the first access to the new window.
After reset, no BUSCON switch waitstates are selected.
User’s Manual
Address (P1)
BUS (P0)
BUS (P0)
ALE
WR
RD
Switching from Demultiplexed to Multiplexed Bus Mode
Demultiplexed
Bus Cycle
Address
Data/Instr.
Data
Idle State
9-7
Figure
Address
Address
9-4.
Figure
Address
Multiplexed
Bus Cycle
9-4).
External Bus Interface
Data/Instr.
C164CM/C164SM
Data
Derivatives
V1.0, 2002-02
MCD02234M