MagTek IntelliStripe 320 99875168 - Manual (Page 7)

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SECTION 1. APPLICATION MESSAGES
This section describes the format of application messages and defines the protocol for using
these messages.
OVERVIEW
Application messages are the blocks of information exchanged between two applications. They
consist of a header and data. The message format and contents are independent of the transport
mechanism by which the messages are exchanged. Each message has a length that is provided
by the transport mechanism for messages being received or is supplied to the transport
mechanism for messages being transmitted. The transport mechanism is outside the scope of this
document.
MESSAGE FORMAT
The following diagram illustrates the message format:
MTYP APPL CMND RC DATA
Message Header
The message header contains four one-byte fields: Message Type, Application ID, Command ID
and Result Code. The header is followed by zero or more bytes of data. The existence and
format of the data depends on the Application ID and Command ID.
The following sections describe each field of the header.
Message Type
This field specifies the message type: request, response or notification. The table below defines
the encoding of the message type:
Bits Value Definition
00 Request message type.
01 Response message type.
10 Notification message type.
7-6
11 Reserved for future use.
5-0 – Reserved for future use.
Requests are the messages sent by a host application to a device application. The device
performs the requested operation and sends a response message to the host application. The
device can service only one request at a time. If a request is pending, no further requests should
be sent to the device until a response is received.