
C165H
Architectural Overview
Data Sheet
36
2001-04-19
PRELMNARY
Pins“) or it can be driven by an external oscillator. The oscillator either directly feeds the
external clock signal to the controller hardware (through buffers), divides the external
clock frequency by 2 or 4, or feeds an on-chip phase locked loop (PLL) which multiplies
the input frequency by a selectable factor
F
. This resulting internal clock signal is also
referred to as “CPU clock”. Two separated clock signals are generated for the CPU itself
and the peripheral part of the chip. While the CPU clock is stopped during the idle mode,
the peripheral clock keeps running. Both clocks are switched off, when the power down
mode is entered.
-EXCERPT-
way. For up to five address areas the bus mode (multiplexed / demultiplexed), the data
bus width (8-bit / 16-bit) and even the length of a bus cycle (waitstates, signal delays)
can be selected independently. This allows to access a variety of memory and peripheral
components directly and with maximum efficiency. If the device does not run in Single
Chip Mode, where no external memory is required, the EBC can control external
accesses in one of the following four different external access modes:
16-/18-/20-/24-bit Addresses, 16-bit Data, Demultiplexed
16-/18-/20-/24-bit Addresses, 8-bit Data, Demultiplexed
16-/18-/20-/24-bit Addresses, 16-bit Data, Multiplexed
16-/18-/20-/24-bit Addresses, 8-bit Data, Multiplexed
The demultiplexed bus modes use PORT1 for addresses and PORT0 for data input/
output. The multiplexed bus modes use PORT0 for both addresses and data input/
output. All modes use Port 4 for the upper address lines (A16...) if selected.
Important timing characteristics of the external bus interface (waitstates, ALE length and
Read/Write Delay) have been made programmable to allow the user the adaption of a
wide range of different types of memories and/or peripherals. Access to very slow
memories or peripherals is supported via a particular 'Ready' function.
For applications which require less than 64 KBytes of address space, a non-segmented
memory model can be selected, where all locations can be addressed by 16 bits, and
thus Port 4 is not needed as an output for the upper address bits (A22/A19/A17...A16),
as is the case when using the segmented memory model.
O
n-chip XBUS
is an internal representation of the external bus and allows to access
integrated application-specific peripherals/modules in the same way as external
components. It provides a defined interface for these customized peripherals.
3.3
Clock Generation Concept
The on-chip clock generator provides the C165H with its basic clock signal that controls
all activities of the controller hardware. Its oscillator can either run with an external crystal
and appropriate oscillator circuitry (see also recommendations in chapter Dedicated