Schneider Automation Modicon Quantum Ethernet Betriebsanweisung PDF herunterladen (Seite 90)

Quantum Ethernet TCP/IP Modbus Application Protocol

840 USE 115 00 Version 1.0

C.2 Modbus Application Protocol PDU Analysis

The Modbus Application Protocol PDU is transmitted over a TCP/IP Ethernet stack.

Both Ethernet II and IEEE 802.3 framin

will be accommodated. Ethernet II

framin

is the default.

. . . from the wire in for IEEE 802.3 framin

. . .

. . . is IEEE 802.3 framin

if len

th <=1500 . . .

802.3_pdu ::= {dst_addr[6], src_addr[6], len

th[2], data=802.2_pdu}

*an IEEE 802.3 PDU has a maxFrameSize of 1518 octets

*an IEEE 802.3 PDU has a minFrameSize of 64 octets

802.2_pdu : {dsap[1], ssap[1], frm_cntrl[1], snap_hdr[5], data=ip_pdu}

*the snap_hdr is associated with a “well-known” 802.2 sap snap_hdr

::={or

_code[3], ethert

pe[2] }

*the snap hdr

(

sub network access protocol

)

allows the older st

Ethernet protocols to run on the newer IEEE 802.2 interface. The

ethert

pe parameter indicates the service, ex. ip or arp. IP has a value

0x800.

. . . from the wire in for Ethernet II framin

. . .

. . . is Ethernet II framin

if len

th >1500 . . .

802.3_pdu ::= {dst_addr[6], src_addr[6], len

th[2], data=ip_pdu}

. . . the common part of the packet be

ins here . . .

ip_pdu ::= {ip_hdr[20], data=tcp_pdu}

tcp_pdu ::= {tcp_hdr[24], data=appl_pdu=mbap_pdu}

The mbap_pdu is the Modbus Application Protocol whose messa

es are received

at a well-known port. The current maximum size of the mbap_pdu for this class of

services in 256 b

tes.

The structure and content of the mbap_pdu is defined to be:

mbap_pdu ::={ inv_id[2], proto_id[2], len[2], dst_idx[1], data=mb_pdu }

1 2 ... 85 86 87 88 89 90 91 92 93 94 95 ... 104 105

Kommentare zu diesen Handbüchern

Keine Kommentare

Schneider Automation Modicon Quantum Ethernet Betriebsanweisung Seite 90

Kommentare zu diesen Handbüchern