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(a) A Start of Message character
(b) One or two address characters (uniquely defining the slave)
(c) A parameter/data character string
(d) An End of Message character
Messages from the master device may be one of four types:
Type 1: L {N} ? ? *
Type 2: L {N} {P} {C} *
Type 3: L {N} {P} # {DATA} *
Type 4: L {N} {P} I *
where all characters are in ASCII code and:
L is the Start of Mes sage char ac ter (Hex 4C)
{N} is the slave ad dress (in the range 1 - 32); ad dresses 1 - 9
may be rep re sented by a sin gle digit (e.g. 7) or in two- digit
form, the first digit be ing zero (e.g. 07).
{P} is a char ac ter which iden ti fies the pa rame ter to be in ter ro -
gated/modi fied - see Ta ble 4-2.
{C} is the com mand (see be low)
# in di cates that {DATA} is to fol low (Hex 23)
{DATA} is a string of nu meri cal data in AS CII code (see Ta ble 4-1)
* is the End of Mes sage char ac ter (Hex 2A)
No space char ac ters are per mit ted in mes sages. Any syn tax er rors in a re ceived
mes sage will cause the slave to is sue no re ply and await the Start of Mes sage
char ac ter.
4-2 November, 2000 OM067-4
Sec tion 4
1
8
-DIN Digi tal In di ca tor 59039
RS485 Se rial Com mu ni ca tions Product Man ual - Vol ume I