RKC INSTRUMENT AE500 - 4 Protocol; Polling

IMAE02-E3
19
4. PROTOCOL
AE500 uses the polling/selecting method to establish a data link. The basic procedure is followed
ANSI X3.28 subcategory 2.5, A4 basic mode data transmission control procedure (Fast selecting is
the selecting method used in this AE500).
zThe polling/selecting procedures are a centralized control method where the host computer
controls the entire process. The host computer initiates all communication so the AE500
responds according to queries and commands from the host.
zThe code use in communication is 7-bit ASCII code including transmission control characters.
The transmission control characters are EOT (04H), ENQ (05H), ACK (06H), NAK (15H), STX
(02H) and ETX (03H). The figures in the parenthesis indicate the corresponding hexadecimal
number.
4.1 Polling
Polling is the action where the host computer requests one of the connected AE500s to transmit data.
An example of the polling procedure is shown below:
Host
computer
send
Host
computer
send
Host com
p
uter send
AE500
send
A
E500 send
E
O
T
E
O
T
[
Data
]
[
BCC
]
[
ID
]
(1)
(2)
(5)
(3)
(4)
(9)
(7)
(10)
[
Address
]
[
ID
]
No res
p
onse
No
response
Indefinite
Time
out
ID: Identifier
E
O
T
E
O
T
S
T
X
A
C
K
N
A
K
E
T
X
E
N
Q
(8)
(6)