GS-C200 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
Manufacturer
GS-C200 Datasheet PDF : 31 Pages
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GS-C200 / GS-C200S
The general format of a command string is the
following:
ADDRESS COMMAND ARGUMENT CHECKSUM CAR.RETURN
The Address must be the first transmitted charac-
ter and it is present only if the Multipoint protocol is
used (at least one of SEL0, SEL1, SEL2 is different
from zero).
The Command is the second character(s) of the
string, in the Multipoint protocol, but it becomes the
transmission opening character when the Point-to-
Point protocol is used (SEL0, SEL1 and SEL2 = 0).
The Argument, if required, is specified immediately
after the command and its length depends on the
command type.
The Checksum character verifies the correctness
of the received string; its value is determined by the
sum of the binary values of the preceding charac-
ters. The result is cut at the seventh least significant
bit and ORed with exadecimal 10 (C200S/C200
from V2.2) to make the result compatible with the
transmission system. The last character, the string
ending character, is always a Carriage Return that
will be identified in the following by the symbol (↓).
By connecting the pin CHS (pin 7) to ground, the
checksum character is not anymore requested, and
the task of guaranteeing the correctness of the
message is left to the parity bit. It should be noted
that by using this dialogue mode, the data integrity
confidence level is reduced. Because motion sys-
tems normally operate in manufacturing premises
subjected to heavy electro-magnetic noise, and
because any communication problem may have
catastrophic effects on the system actions, it is a
good practice to use the checksum character when-
ever possible. The checksum character is normally
not used (pin CHS connected to ground) when the
GS-C is connected to a video-terminal, i.e. during
the initial programming and debugging phase. In
the following, three examples of command strings
sent to a GS-C module are given.
Example 1 - MULTIPOINT PROTOCOL. The Host
Computer wants to set the USER output 3 of the
module #2. The command will have the following
format:
2A36↓
Carriage return
Checksum
Address Command
Module #2 Activate
Argument
USER out 3
The checksum character 6 results from the binary
sum of the character 2 (ASCII value = 32) + char-
acter A (ASCII value = 41) + character 3 (ASCII
value = 33) truncated at the seventh bit.
Example 2 - POINT-TO-POINT PROTOCOL.
The same instruction is given by the Host to a Point
to Point connected module.
The command will have the following format:
A3t↓
The checksum character has an ASCII value t that
derives from the sum of the ASCII code A+3 = 41+33
= 74 in binary weighted code or t in ASCII code.
Example 3 - POINT-TO-POINT PROTOCOL
WITHOUT CHECKSUM.
For the same instruction, the command format will
be:
A3↓
The string consists of command and argument only.
The GS-C feeds back information to the Host every
time it receives a command, therefore it has not to
identify itself to the Host when answering in a
Multipoint connection.
The format of the string answered back by the GS-C
is the following:
ANSW.CODE ARGUMENT CHECKSUM CAR.RETURN
The first character, which always identifies the an-
swer type, may assume one of the following values:
Y The command string has been correctly
r ec ei ved.
B The controller is Busy and cannot process
commands.
R The controller is Ready to process commands.
E An error has been detected. The type of error
is specified by the number following the ”E”.
V A controller status (a position or an USER
input/output status) is sent back and its value
is specified by the characters following the ”V”.
The length of the Argument, present only for ”E” and
”V” answers, can range between 1 and 7 charac-
ters, and it is a function of the received command.
The number following the ”E” code, i.e. the error
argument, specifies the detected error type accord-
ing to the following table:
10/31
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