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November 2005 1/97
This is advanced information from STMicroelectronics. Details are subject to change without notice.
Rev. 2
ST7 FAMILY
PROGRAMMING MANUAL
INTRODUCTION
The ST7 family of HCMOS Microcontrollers has
been designed and built around an industry stand
-
ard 8-bit core and a library of peripheral blocks,
which include ROM, EPROM, RAM, EEPROM, I/
O, Serial Interfaces (SPI, SCI, I2C,...), 16-bit Tim
-
ers, etc. These blocks may be assembled in vari-
ous combinations in order to provide cost-effective
solutions for application dedicated products.
The ST7 family forms part of the STMicroelectron-
ics 8-bit MCU product line, and finds place in a
wide variety of applications such as automotive
systems, remote controls, video monitors, car ra
-
dio and numerous other consumer, industrial, tel-
ecom, multimedia and automotive products.
ST7 ARCHITECTURE
The 8-bit ST7 Core is designed for high code effi-
ciency. It contains 6 internal registers, 17 main ad-
dressing modes and 63 instructions. The 6 inter-
nal registers include 2 Index registers, an Accu-
mulator, a 16-bit Program Counter, a Stack Point-
er and a Condition Code register. The two Index
registers X and Y enable Indexed Addressing
modes with or without offset, along with read-mod
-
ify-write type data manipulations. These registers
simplify branching routines and data modifica
-
tions.
The 16-bit Program Counter is able to address up
to 64K of ROM / EPROM memory. The 6-bit Stack
Pointer provides access to a 64-level Stack and
an upgrade to an 8-bit Stack Pointer is foreseen in
order to be able to manage a 256-level Stack. The
Core also includes a Condition Code Register pro
-
viding 5 Condition Flags that indicate the result of
the last instruction executed.
The 17 main Addressing modes, including Indirect
Relative and Indexed addressing, allow sophisti
-
cated branching routines or CASE-type functions.
The Indexed Indirect Addressing mode, for in
-
stance, permits look-up tables to be located any-
where in the address space, thus enabling very
flexible programming and compact C-based code.
The 63-instruction Instruction Set is 8-bit oriented
with a 2-byte average instruction size. This In
-
struction Set offers, in addition to standard data
movement and logic
/arithmetic functions, byte
multiplication, bit manipulation, data transfer be
-
tween Stack and Accumulator (Push / Pop) with di-
rect stack access, as well as data transfer using
the X and Y registers.
Depending of the target device, different methods
of Interrupt priority management may be selected:
the number of Interrupt vectors can vary from 6 to
16, and the priority level may be managed by soft
-
ware on some versions. Some peripherals include
Direct Memory Access (DMA) between serial in
-
terfaces and memory.
Power-saving may be managed under program
control by placing the device in WAIT or HALT
mode.
A high test coverage is achieved for ST 7 family
devices thanks to the use of an autotest method
based on "Cyclic Redundancy Checking" (CRC).
This approach is based on the analysis of a data
flow comprising not only input and output, but also
internal data, which affords a detailed inside view
of the behaviour of the core and of the peripherals.
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