
User Manual
C166S V2
C166S V2 Memory Organization
User Manual
3-98
V 1.7, 2001-01
subsequent word registers, with the source pointer (SRCPx) on the lower and the
destination pointer (DSTPx) on the higher word address (x = channel number). The PEC
registers are part of the PEC itself and are addressed via the internal peripheral bus.
In contrast to the C166 family, the pointers are not located in the internal RAM. The
pointers are located in the 4 kByte internal IO.
If a PEC channel is not used, the corresponding pointer locations are not available and
cannot be used for word and byte storage.
Writing to any byte of the PEC pointers does cause the non-addressed complementary
byte to be cleared!
For more detail about use of the source and destination pointers for PEC data transfer,
see the
“
Interrupt and Exception Execution
”
section.
3.4
External Memory Space
The C166S V2 CPU is capable of using an address space of up to 16 MBytes. Only
portions of this address space are occupied by internal memory areas. All addresses not
used for on-chip memory or for registers may reference external memory locations. This
external memory is accessed via the external bus interface. This interface may further
limit the amount of addressable external memory.
External word and byte data can be accessed only via indirect or long 16-bit addressing
modes using one of the four DPP registers. There is no short addressing mode for
external operands. Any word data access is made to an even byte address and double
word accesses to modulo 4 byte addresses (even word address).
The external memory is not provided for single bit storage and therefore is not bit
addressable.
3.4.1
Boot and Debug/Monitor Program Memories
The 64 KByte memory area of segment 191 (BF
’
0000
H
...BF
’
FFFF
H
) is reserved for boot
and debug/monitor program memories. These
“
on chip
”
memories are accessed using
the EBC and are a part of the EBC
‘
s external memory space. Accesses are not visible
at the port pins of the EBC even if these memories are part of the external memory
space. During normal code execution, this segment is not accessible for the C166S V2
CPU. In case of a read access, the EBC will deliver the predefined 0000
H
value and write
access will not be executed. Only in special boot and emulation modes can the
memories of segment 191 be accessed.
Note: Segment 191 (BF
’
0000
H
...BF
’
FFFF
H
) is not usable for the system application.
External memories and peripherals located in this segment will never be
accessed.