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C165UTAH
Architectural Overview
Data Sheet
35
2001-02-23
a memory table. The C165UTAH has 8 PEC channels each of which offers such fast
interrupt-driven data transfer capabilities.
Memory Areas
The memory space of the C165UTAH is configured in a Von Neumann architecture
which means that code memory, data memory, registers and I/O ports are organized
within the same linear address space which covers up to 8 MBytes. The entire memory
space can be accessed bytewise or wordwise. Particular portions of the on-chip memory
have additionally been made directly bit addressable.
A 16-bit wide internal RAM (IRAM)
provides fast access to General Purpose Registers
(GPRs), user data (variables) and system stack. The internal RAM may also be used for
code. A unique decoding scheme provides flexible user register banks in the internal
memory while optimizing the remaining RAM for user data. The size of the internal RAM
is 3 KByte.
The CPU disposes of an actual register context consisting of up to 16 wordwide and/or
bytewide GPRs, which are physically located within the on-chip RAM area. A Context
Pointer (CP) register determines the base address of the active register bank to be
accessed by the CPU at a time. The number of register banks is only restricted by the
available internal RAM space. For easy parameter passing, a register bank may overlap
others.
A system stack of up to 1024 words is provided as a storage for temporary data. The
system stack is also located within the on-chip RAM area, and it is accessed by the CPU
via the stack pointer (SP) register. Two separate SFRs, STKOV and STKUN, are
implicitly compared against the stack pointer value upon each stack access for the
detection of a stack overflow or underflow.
Hardware detection of the selected memory space is placed at the internal memory
decoders and allows the user to specify any address directly or indirectly and obtain the
desired data without using temporary registers or special instructions.
For Special Function Registers
1024 Bytes of the address space are reserved. The
standard Special Function Register area (SFR) uses 512 bytes, while the Extended
Special Function Register area (ESFR) uses the other 512 bytes. (E)SFRs are wordwide
registers which are used for controlling and monitoring functions of the different on-chip
units. Unused (E)SFR addresses are reserved for future members of the C165UTAH
family with enhanced functionality.
External Bus Interface
In order to meet the needs of designs where more memory is required than is provided
on chip, up to 8 MBytes of external RAM and/or ROM can be connected to the
microcontroller via its external bus interface. The integrated External Bus Controller
(EBC) allows to access external memory and/or peripheral resources in a very flexible