Hardware Reference
In-Depth Information
MC
9
S12
Dx
256
B
xx
x
Packaging
designator
Status of product:
MC = fully qualified
XC = partially qualified
PC = product engineering
KMC = sample pack
KXC = sample pack
Temperature range
C = - 40°C to 85°C
V = - 40°C to 105°C
M = - 40°C to 125°C
Memory type
9 = flash
Flash
rev.
Core
type
Approximate
memory
Family
Figure 1.9
■
Freescale product numbering system for the HCS12
devices also include a certain amount of on-chip SRAM and EEPROM to hold data and/or pro-
grams needed in different applications.
Most HCS12 devices have many I/O pins to interface with I/O devices. When on-chip
memory is not adequate, external memory can be added. All HCS12 devices adopt the same
design for the same peripheral function to facilitate the migration from one device (with less
memory or fewer peripheral functions) to another.
The features of all HCS12 devices are shown in Appendix C. All devices with the CAN module
are for automotive applications. The numbering system for the HCS12 is shown in Figure 1.9.
In addition to automotive and control applications, Freescale is also trying to attract users from
other application areas. For example, the MC9S12NE64 was designed for applications that need to
access the Internet whereas the MC9S12UF32 was designed for interfacing with the USB bus.
Software debugging support is an important issue for embedded applications. Freescale has
implemented the Background Debug Mode (BDM) in each HCS12 member. With this BDM
module, the tool developers can design inexpensive software debugging tools for the HCS12.
Most of the HCS12 features and peripheral functions will be discussed in this text.
The HCS12 microcontroller has registers for supporting general-purpose operations and
controlling the functioning of peripheral modules. These registers are divided into two categories:
CPU registers and I/O registers. CPU registers are used solely to perform general-purpose operations
such as arithmetic, logic, and program flow control. I/O registers are mainly used to configure the
operations of peripheral functions, to hold data transferred in and out of the peripheral subsystem,
and to record the status of I/O operations. The I/O registers in a microcontroller can further be clas-
sified into
data
,
data
direction
,
control
, and
status registers
. These registers are treated as memory
locations when they are accessed. CPU registers do not occupy the HCS12 memory space.
The CPU registers of the HCS12 are shown in Figure 1.10 and are listed next. Some of the
registers are 8 bit and others are 16 bit.
General-purpose accumulators A and B.
Both A and B are 8-bit registers. Most arithme-
tic functions are performed on these two registers. These two accumulators can also be
concatenated to form a single, 16-bit accumulator referred to as the D accumulator.
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