5-4
MK1000 MicroKiosk Product Reference Guide
Host to MK1000 Handshaking
ACK/NAK handshaking is supported for data sent from the h ost to the MK1000. If enabled,
the MK1000 ACKs or NAKs a data packet based on its format and the LRC being correct.
Because no error checking is performed on the data in the pack et, the MK1000 ignores
invalid display commands within the packet and s ends an ACK.
This increases the throughput of the system. The MK1000 ca n store incoming packets in
memory while performing commands in packets already received. This f rees up the host to
do other things after sending a sequence of complex comman ds to the MK1000. The
MK1000 can store up to 25 packets (totaling up to 600 bytes) in memory befor e the queue
is full. When full, incoming packets are NAKed until space is avail able (if host to MK1000
ACK/NAK handshaking is enabled).
When the MK1000 is responding to a packet from the host, it wai ts a programmable
Turnaround Time after the last character is received before transmitting back to the ho st.

None

The MK1000 transmits data to the host without software handshaking an d assumes an
ACK. The EOT character is sent immediately after the LRC. Host ha ndshaking is ignored.

ACK/NAK

ACK/NAK is the default software handshaking. The host verifi es the LRC and responds
with an ACK or NAK. If no response is received within the Serial Response Time-out period
(2.0 seconds), a NAK is assumed and the MK1 000 retransmits (see Example 4 - Host Not
Receiving Transmission on page 5-5.) Retransmission occurs up to three times. If a NAK
is received from the host, the MK1000 re-transmits immediately.
If ACK/NAK is disabled, the MK1000 transmits the data and assumes an A CK. The EOT is
sent immediately after LRC.

ENQ (RS-232 Only)

ENQ software handshaking is also supported for data sent to the host. The MK100 0 waits
for an ENQ from the host before sending data. If the ENQ i s not received within the Serial
Response Time-out period (2.0 seconds), the data is discarded.

ACK/NAK with ENQ

The MK1000 uses ACK/NAK handshaking to communicate wi th the host but does not
respond to the host until an ENQ is received.