Installation guide

6: Programming Considerations
DC 900-1564A 91
6.4.3.4 Message Characteristics Identifier (MCI)
The message characteristics identifier field is required in each SLC message sent or
received on a high-level SLC network. Shown as the
mci field in Figure 6–2 on page 89,
the MCI contains one byte, and immediately follows the HEN. The MCI specifies the
nature of the message information content and coding. The SLC protocol service on the
ICP validates the coding of the MCI, but otherwise ignores the content of this field.
Table 6–4 shows the internal format of the
mci field. See also the slc_blks.h “C” include
file.
Table 6–4: Message Characteristics Identifier (MCI) on High-level Networks
Message Characteristics Identifier (MCI) — One Character
MCI_BASE_VALUE Always set
MCI_FORMAT_MASK Mask to isolate (&) or ignore (&~) Format bit-field
MCI_FORMAT_CONVENTIONAL Format bit-field value
MCI_FORMAT_CONVERSATIONAL Format bit-field value
MCI_FORMAT_HOST_TO_HOST Format bit-field value
MCI_FORMAT_NETWORK_CONTROL Format bit-field value
MCI_INQUIRY Indicates inquiry when set (response when zero)
MCI_CODE_CONVERSION_MASK Mask to isolate (&) or ignore (&~) Code bit-field
MCI_CODE_5BIT_PADDED Code bit-field value
MCI_CODE_6BIT_PADDED Code bit-field value
MCI_CODE_7BIT Code bit-field value
MCI_MESSAGE_REJECTED Indicates rejected message when set (normal status when zero)