Intel 80C196KB Series, Руководство пользователя, Страница: 8 / 98

80C196KB USER’S GUIDE
(CLKOUT) signal, shown in Figure 1-3, is provided as
an indication of the internal machine state. Details on
timing relationships can be found in Section 13.
270651 – 3
Figure 1-3. Internal Clock Waveforms
2.0 MEMORY SPACE
The addressable memory space on the 80C196KB con-
sists of 64K bytes, most of which is available to the user
for program or data memory. Locations which have
special purposes are 0000H through 00FFH and
1FFEH through 2080H. All other locations can be
used for either program or data storage or for memory
mapped peripherals. A memory map is shown in Figure
2-1.
EXTERNAL MEMORY OR I/O
0FFFFH
4000H
INTERNAL ROM/EPROM OR
EXTERNAL MEMORY *
2080H
RESERVED
2040H
UPPER 8 INTERRUPT VECTORS
(NEW ON 80C196KB)
2030H
ROM/EPROM SECURITY KEY
2020H
RESERVED
2019H
CHIP CONFIGURATION BYTE
2018H
RESERVED
2014H
LOWER 8 INTERRUPT VECTORS
PLUS 2 SPECIAL INTERRUPTS
2000H
PORT 3 AND PORT 4
1FFEH
EXTERNAL MEMORY OR I/O
0100H
INTERNAL DATA MEMORY - REGISTER FILE
(STACK POINTER, RAM AND SFRS)
EXTERNAL PROGRAM CODE MEMORY
0000H
Figure 2-1. 80C196KB Memory Map
2.1 Register File
Locations 00H through 0FFH contain the Register File
and Special Function Registers, (SFRs). The RALU
can operate on any of these 256 internal register loca-
tions, but code can not be executed from them. If an
attempt to execute instructions from locations 000H
through 0FFH is made, the instructions will be fetched
from
external
memory. This section of external memo-
ry is reserved for use by Intel development tools
The internal RAM from location 018H (24 decimal) to
0FFH is the Register File. It contains 232 bytes of
RAM which can be accessed as bytes (8 bits), words
(16 bits), or double-words (32 bits). Since each of these
locations can be used by the RALU, there are essential-
ly 232 ‘‘accumulators’’. This memory region, as well as
the status of the majority of the chip, is kept intact
while the chip is in the Powerdown Mode. Details on
Powerdown Mode are discussed in Section 14.
Locations 18H and 19H contain the stack pointer.
These are not SFRs and may be used as standard RAM
if stack operations are not being performed. Since the
stack pointer is in this area, the RALU can easily oper-
ate on it. The stack pointer must be initialized by the
user program and can point anywhere in the 64K mem-
ory space. Operations to the stack cause it to build
down, so the stack pointer should be initialized to 2
bytes above the highest stack location, and must be
word aligned.
2.2 Special Function Registers
Locations 00H through 17H are the I/O control regis-
ters or SFRs. All of the peripheral devices on the
80C196KB (except Ports 3 and 4) are controlled
through these registers. As shown in Figure 2-2, three
SFR windows are provided on the 80C196KB.
Switching between the windows is done using the Win-
dow Select Register (WSR) at location 14H in all of the
windows. The PUSHA and POPA instructions push
and pop the WSR so it is easy to change between win-
dows. Only three values may be written to the WSR, 0,
14 and 15. Other values are reserved for use in future
parts and will cause unpredictable operation.
Window 0, the register window selected with WSR
e
0,
is a superset of the one used on the 8096BH. As depict-
ed in Figure 2-3, it has 24 registers, some of which have
different functions when read than when written. Reg-
isters which are new to the 80C196KB or have changed
functions from the 8096 are indicated in the figure.
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