CCJ1MUNICATIONS SECTION 6, 6
6, 6, 3 SLAVE, HUNTER TO HOST TRANSMISSION
TRANSMISSION
6,6,4
6.6.5
Vim, V09P
It should be noted that following the host transmitting an XOFF,
it is possible, depending on data link speed, to have a further
two characters sent out by HUNTER. This is due to the time
taken to receive the XOFF and the possibility of just missing
the start of the next character.
At the start of transmission a received XON is assumed, to avoid
lock-up.
ETX/ACK
RECEPTION
In this protocol HUNTER will send an ACK character (06 Decimal
or Control F) after reception of an ETX character terminating a
line that has been ready by Basic, The ETX is stripped from
incoming data and not sent to Basic, This protocol causes the
host device to wait at the end of each block of data, which
should not exceed 130 characters, for an acknowledgement that
the block has been read. The ETX/ ACK acknowledgement is only
transmitted when the block has been fetched from the buffer by
Basic,
TRANSMISSION
This protocol will send out an ETX (03 Decimal or Control C)
character after any transmitted carriage return. Transmission
is then halted until an ACK (06 Decimal or Control F) is
received from the host. This enables individual data blocks to
be sent and an acknowledgement awaited. If transmission is to
another HUNTER the blocks should not exceed 130 characters or
the input buffer may be exceeded, If an ACK is not received
within thirty seconds then communication failure is assumed and
an error message is put up on the screen.
The ACKs are not returned to the user program.
By the very nature of this protocol, indeterminate handsh;;iking
situations may occur if any conditions are altered during
transmission.
ACK/NAK
RECEPTION
In this mode HUNTER will receive a complete block of data,
terminated with a carriage return. It will then check for
parity errors. If one exists then a NAK (21 Decimal or Control
U) is sent out to the host and the data block ignored.
PAGE 6 - lll
To Next Page
Loading...