User Manual

42 Creating a LonTalk Stack Serial MIP Driver

Type Code Values

The following table lists the values for the Type Code byte. Uplink means that

data is transferred from the Echelon Smart Transceiver or Neuron Chip to the

host processor. Downlink mans that data is transferred from the host processor

to the Echelon Smart Transceiver or Neuron Chip.

Value Type Description Uplink /

Downlink

0 CpNull No data is being sent. Use this value for

acknowledge-only packets, or for pinging.

U/D

1 CpFail The previous transfer was broken or in

error. This is typically due to checksum

errors or fragmented transfers. The

correct response to this command is to

resend the previous transfer.

U/D

2 CpMsg One message follows. A message is any

multi-byte network interface transfer and

requires an application output buffer or

packet buffer in the downlink case. The

number of messages is stored in the

Param Data field.

This value is limited to one in both the

downlink and uplink case.

The message follows the code packet

checksum byte, and consists of a length

byte, the NI command, the message itself,

and a checksum.

U/D

3 CpMsgReq Optional. Sent by the host for requesting

both the attention of the Serial MIP and

requesting an uplink CpMsgAck.

The Param Data field contains either a 0

or a 1 informing the Serial MIP that the

following message is either a non-priority

message (0) or a priority message (1).

The MIP Serial driver does not use

priority messaging; therefore, this value

is ignored. This allows the Serial MIP to

respond to the CpMsgReq based on

actual buffer availability.

Alternatively, you can send the entire

CpMsg plus message to the MIP and a

CpMsgReject may be sent uplink if

there are no available buffers.