10 Hostmode
153
•
#170#170 ALWAYS leads to a
start of packet
condition, under all situations. The
next byte is then appropriately interpreted as the channel number. (However after a
start of packet is recognized, two #170 in a row must follow so that this
exception
can
work again. This would be in the case #170#170#170...)
10.9.6
Start of the CRC-hostmode
•
The command that switches a TNC/PTC into hostmode is <ESC>JHOST4<CR>.
•
After the start of the CRC-hostmode, the internal REQUEST-bit in the SLAVE (PTC)
should be set to
not defined
so that either 1 or 0 are valid as REQUEST-BIT in the
first transmit packet from the MASTER. Thus when the CRC is correct at the
SLAVE, an ACK-condition follows. Independent of the above, it is recommended
that the first transmit packet from the MASTER, after a hostmode start, or program
start, should have bit 6 set, to ensure that a correctly received packet at the SLAVE
always leads to an ACK-condition. (This allows the MASTER to start the protocol
without having to know the condition of the (old) buffered RQ-flags at the SLAVE.)