CCJ1MUNICATIONS
SECTION 6.6
6.6.6
6.6,6, 1
VER.V0.9F
If the block is error-free then the received block is sent
character by character to Basic, When the carriage return is
sent to Basic an ACK (06 Decimal or Control F) is sent out to
the host to indicate successful data block reception,
TRANSMISSION
Data blocks are first placed into a transmission buffer, Upon
receipt of a carriage return from Basic, the entire buffer is
transmitted, HUNTER then awaits an acknowledgement.
If an ACK
is received then the next data block is assembled into the
buffer and sent. If a NAK (21 Decimal or Control U) is received
then a failure is indicated and the entire buffer is sent again.
If nothing is received after three seconds a NAK is assumed and
the buffer sent again. The NAKs may be sent a maximum of three
times. If an ACK is still not received then the communications
failure message is put on the screen,
SYSTIME
HUNTER to Systime communications Protocol Specification
This protocol is provided to facilitate communication between
HUNTER and Systime model S500 minicomputers, The protocol
embodies a checksum in addition to parity checks,
Data is sent in the form of messages which are subdivided into
one or more fixed length blocks. Each block is individually
checked and acknowledged before any further blocks are sent,
DATA BLOCKS
Each block consists of:-
1 start character
64 data characters
3 checksum
1 stop character
The purpose of each character group is as follows:-
Start Character
The first block of a message uses SOH (01 Decimal). Further
blocks use STX (02H) as the start character.
Stop Character
The last block of a message uses EOT (04 Decimal), previous
blocks use ETX (03H) as the stop character.
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