Z80382 Datasheet, PDF (37/77 Pages) Zilog, Inc. – HIGH-PERFORMANCE DATA COMMUNICATIONS PROCESSORS

Zilog
Z80382/Z8L382
High-Performance Data Communications Processors
4 Sets of Registers
A
F
1
BCz
B
C
DEz
D
E
HLz
H
L
IXz
IXU
IXL
IYz
IYU
IYL
BCz'
DEz'
HLz'
IXz'
IYz'
A'
F'
B'
C'
D'
E'
H'
L'
IXU'
IXL'
IYU'
IYL'
R
Iz
I
SPz
SP
PCz
PC
Figure 22. 380C Processor Core Register Set
Stack Pointer. The Stack Pointer (SP) is used for saving
information when an interrupt or trap occurs and for sup-
porting subroutine calls and returns. Stack Pointer relative
addressing allows parameter passing using the SP.
Select Register. The Select Register (SR) controls the
register set selection and the operating modes of the 380C
CPU.
CPU Control Register Space
The CPU control register space consists of the 32-bit Se-
lect Register (SR). The contents of SR determine the CPU
operating mode, which register bank will be used, the in-
terrupt mode in effect, and other items of this type.
Memory Address Space
The memory address space can be viewed as a linear
space of 4 GB. The actual usable memory space in the
Z382, however, is 16 MB, since only the lower 24 bits of
the address are output on the external address bus. The 8-
bit byte is the basic addressable element in the 380C
memory address space. However, there are other addres-
sable data elements; bits, 2-byte words, byte strings, and
4-byte words. The size of the data element being ad-
dressed depends on the instruction being executed as well
as the Word/Long Word mode.
When a word is stored in memory, the least significant byte
precedes the more significant byte of the word, as in the
Z80 CPU architecture. Also, the lower-addressed byte is
present on the upper byte of the external data bus.
On-Chip and External I/O Address Space
The 380C CPU architecture distinguishes between the
memory and I/O spaces and, therefore, requires specific
I/O instructions. I/O instructions are used to access the
Z382Õs internal peripherals as well as a number of control
registers which deal with functions such as interrupts and
traps. I/O instructions are also used to access external pe-
ripheral controllers connected to the Z382Õs external ad-
dress, data and control busses.
Data Types
The Z380 CPU can operate on bits, Binary-Coded Decimal
(BCD) digits (4 bits), bytes (8 bits), words (16 bits or 32
bits), byte strings, and word strings. Bits in registers can be
set, cleared, and tested. BCD digits, packed two to a byte,
can be manipulated with the Decimal Adjust Accumulator
instruction (in conjunction with binary addition and subtrac-
DS97Z382000
PRELIMINARY
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