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C165UTAH
Architectural Overview
Data Sheet
41
2001-02-23
3.4
On-Chip Peripheral Blocks
The C165UTAH clearly separates peripherals from the core. This structure permits the
maximum number of operations to be performed in parallel and allows peripherals to be
added or deleted from family members without modifications to the core. Each functional
block processes data independently and communicates information over common
buses. Peripherals are controlled by data written to the respective Special Function
Registers (SFRs). These SFRs are located either within the standard SFR area
(00’FE00
H
...00’FFFF
H
) or within the extended ESFR area (00’F000
H
...00’F1FF
H
).
These built in peripherals either allow the CPU to interface with the external world, or
provide functions on-chip that otherwise were to be added externally in the respective
system.
The C165UTAH peripherals are:
Two General Purpose Timer Blocks (GPT1 and GPT2)
An Asynchronous/Synchronous Serial Interface (ASC)
A High-Speed Synchronous Serial Interface (SSC)
An Universal Serial Bus Interface (USB)
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