Intel 80C196KB Series, Руководство пользователя, Страница: 13 / 98

80C196KB USER’S GUIDE
The 80C196KB provides a ROM/EPROM lock feature
to allow the program to be locked against reading
and/or writing the internal program memory. In order
to maintain security, code can not be executed out of
the last three locations of internal ROM/EPROM if
the lock is enabled. Details on this feature are in Sec-
tion 17.
2.5 System Bus
There are several modes of system bus operation on the
80C196KB. The standard bus mode uses a 16-bit multi-
plexed address/data bus. Other bus modes include an
8-bit mode and a mode in which the bus size can dy-
namically be switched between 8-bits and 16-bits.
Hold/Hold Acknowledge (HOLD/HLDA) and Ready
signals are available to create a variety of memory sys-
tems. The READY line extends the width of the RD
(read) and WR (write) pulses to allow access of slow
memories. Multiple processor systems with shared
memory can be designed using HOLD/HLDA to keep
the 80C196KB off the bus. Details on the System Bus
are in Section 15.
3.0 SOFTWARE OVERVIEW
This section provides information on writing programs
to execute in the 80C196KB. Additional information
can be found in the following documents:
MCS
É
-96 MACRO ASSEMBLER USER’S GUIDE
Order Number 122048 (Intel Systems)
Order Number 122351 (DOS Systems)
MCS
É
-96 UTILITIES USER’S GUIDE
Order Number 122049 (Intel Systems)
Order Number 122356 (DOS Systems)
PL/M-96 USER’S GUIDE
Order Number 122134 (Intel Systems)
Order Number 122361 (DOS Systems)
C-96 USER’S GUIDE
Order Number 167632 (DOS Systems)
Throughout this chapter short sections of code are used
to illustrate the operation of the device. For these sec-
tions it is assumed that the following set of temporary
registers has been declared:
AX, BX, CX, and DX are 16-bit registers.
AL is the low byte of AX, AH is the high byte.
BL is the low byte of BX
CL is the low byte of CX
DL is the low byte of DX
These are the same as the names for the general data
registers used in the 8086. It is important to note that in
the 80C196KB these are not dedicated registers but
merely the symbolic names assigned by the program-
mer to an eight byte region within the on-board register
file.
3.1 Operand Types
The MCS-96 architecture supports a variety of data
types likely to be useful in a control application. To
avoid confusion, the name of an operand type is capital-
ized. A ‘‘BYTE’’ is an unsigned eight bit variable; a
‘‘byte’’ is an eight bit unit of data of any type.
BYTES
BYTES are unsigned 8-bit variables which can take on
the values between 0 and 255. Arithmetic and relational
operators can be applied to BYTE operands but the
result must be interpreted in modulo 256 arithmetic.
Logical operations on BYTES are applied bitwise. Bits
within BYTES are labeled from 0 to 7, with 0 being the
least significant bit.
WORDS
WORDS are unsigned 16-bit variables which can take
on the values between 0 and 65535. Arithmetic and
relational operators can be applied to WORD operands
but the result must be interpreted modulo 65536. Logi-
cal operations on WORDS are applied bitwise. Bits
within words are labeled from 0 to 15 with 0 being the
least significant bit. WORDS must be aligned at even
byte boundaries in the MCS-96 address space. The least
significant byte of the WORD is in the even byte ad-
dress and the most significant byte is in the next higher
(odd) address. The address of a word is the address of
its least significant byte. Word operations to odd ad-
dresses are not guaranteed to operate in a consistent
manner.
SHORT-INTEGERS
SHORT-INTEGERS are 8-bit signed variables which
can take on the values between
b
128 and
a
127.
Arithmetic operations which generate results outside of
the range of a SHORT-INTEGER will set the overflow
indicators in the program status word. The actual nu-
meric result returned will be the same as the equivalent
operation on BYTE variables.
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数控原理与维修
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