Siemens MOBY I ASM 421 Technical Description page 5

ASM 421 Technical Description
Similarities between MOBY file handler and a floppy disk
– The user does not access physical memory addresses
– The user addresses the data via logical names, which consist of up to eight letters
– The conversion of the logical names into physical memory addresses is carried out by software
in the interface module:
File handler
– Contiguous data blocks are called files
– The management of files of differing lengths is carried out by a software procedure (file handler)
– The memory is divided into 3 areas:
System area
Directory
User data
Advantages of the file handler for the MOBY I user.
– When specifying a system, it is only necessary to define the names (file names) of the individual
data objects that are to be stored on the MDS.
– The project engineer does not need to structure MDS memory at all.
– The list of data objects can be changed or extended as required during detailed planning. The
MDS data structure does not need to be taken into account.
– The lengths of the individual data objects do not need to be known.
– The description of each data object is a name of up to eight letters. The choice of name can be
directly related to the object (e.g., WORKSNO; SERIALNO; QUALITY; ADDRESS; ORDER;
Drillprog; Turnprog; Millprog;...)
– The programmer does not need to work with absolute addresses. Several sources of program-
ming errors are thus excluded (e.g. double addressing, input errors leading to wrong addresses
and file lengths). The file handler converts the file names into physical MDS addresses.
– Details of the files stored on the MDS can be requested by the "directory" command.
– Data objects can be accessed simply and rapidly using the STG 4F service and test unit. This is
of great advantage to commissioning and maintenance personnel.
– The documentation of the MDS memory structure is very simple and easy to understand, con-
sisting only of a list of file names.
– The user can allocate access rights. Unauthorized deletion and overwriting of user data is thus
avoided.
6GT2 002-0DA00 ASM 421 / V.24
6GT2 002-0DB00 ASM 421 / RS422
6GT2 002-0DC00 ASM 421 / TTY
Disk-Operating-System (DOS)
The system area contains general system data:
– Volume name
– Format and size of memory
– Data coding
All file names and file lengths are stored in the directory. The file handler calculates
the physical addresses of the user data from these entries.
The largest memory area is reserved for user data, which can be stored in any
form (ASCII, binary, hexadecimal, decimal, etc.). The user data is managed by the
file handler in blocks. On a floppy, these blocks are known as "sectors" or "logical
blocks".
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6GT2 097-3AH00-0DA2
Subject to change without notice!
RD: 03/02
J31069-D0142-U001-A0-7618