
C165H
Architectural Overview
Data Sheet
41
2001-04-19
PRELMNARY
When an SFR is written to by software in the same state where it is also to be modified
by the peripheral, the software write operation has priority. Further details on peripheral
timing are included in the specific sections about each peripheral.
-EXCERPT-
C165H peripherals are:
Two General Purpose Timer Blocks (GPT1 and GPT2)
An Asynchronous/Synchronous Serial Interface (ASC)
A High-Speed Synchronous Serial Interface (SSC)
An IOM-2 Interface (IOM-2)
A Watchdog Timer (WDT)
Seven I/O ports with a total of 72 I/O lines
Each peripheral also contains a set of Special Function Registers (SFRs), which control
the functionality of the peripheral and temporarily store intermediate data results. Each
peripheral has an associated set of status flags. Individually selected clock signals are
generated for each peripheral from binary multiples of the CPU clock.
Peripheral Interfaces
The on-chip peripherals generally have two different types of interfaces, an interface to
the CPU and an interface to external hardware. Communication between CPU and
peripherals is performed through Special Function Registers (SFRs) and interrupts. The
SFRs serve as control/status and data registers for the peripherals. Interrupt requests
are generated by the peripherals based on specific events which occur during their
operation (eg. operation complete, error, etc.).
For interfacing with external hardware, specific pins of the parallel ports are used, when
an input or output function has been selected for a peripheral. During this time, the port
pins are controlled by the peripheral (when used as outputs) or by the external hardware
which controls the peripheral (when used as inputs). This is called the 'alternate (input
or output) function' of a port pin, in contrast to its function as a general purpose I/O pin.
Peripheral Timing
Internal operation of CPU and peripherals is based on the CPU clock (f
CPU
). The on-chip
oscillator derives the CPU clock from the crystal or from the external clock signal. The
clock signal which is gated to the peripherals is independent from the clock signal which
feeds the CPU. During Idle mode the CPU’s clock is stopped while the peripherals
Programming Hints
Access to SFRs
All SFRs reside in data page 3 of the memory space. The following addressing
mechanisms allow to access the SFRs: