Siemens SIMATIC NET SPC 4-2 LF, Manual

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PROFIBUS Controller SPC 4®-2 LF
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C79000-G8976-C157-3
11.1 Universal Processor Interface
Description
The SPC 4-2 has a parallel 8-bit interface with a 10-bit address bus. It supports all
8-bit microcontrollers whose CPU is based on the 80C51/52 (80C32) line from
INTEL, the MOTOROLA HC11 family, and the 8/16-bit microcontroller of the
80C166 family from SIEMENS, X86-compatable processors from Intel and the
HC16 and HC916 family from MOTOROLA.
A clock divider is also integrated that provides the internal working clock rate
divided by 2 or 4 for external use and therefore allows low-cost systems to be
implemented.
Since the data formats of Intel and Motorola processors are not compatible, the
SPC 4-2 automatically performs
'byte swapping' when access is in words (only
when writing or reading a 16-bit register in the parameter area; all other
parameters must be accessed byte-oriented)
. This allows a Motorola processor
to read the 16-bit value correctly. As usual, reading or writing requires two
accesses (8-bit data bus). With the two configuration pins TYPE and MODE, the
interface can support the different microcontroller types and their bus timing as
required (read and write cycles). . The TYPE pin decides the data format for the
microcontroller family and the MODE pin decides synchronous (rigid) or
asynchronous bus timing. The "divider" pin can also be used to set a clock rate
divided by 2 or 4 at the ISCLK-Out pin.