This read-write integer is the connection's Minimum Cell Rate, derived from the mir object if not explicitly provided during connection setup; on FRSM12 the description states its default is frConnPCR. An administrator can override it directly, but by default it is tied to whichever minimum-rate parameter the card type derives it from. For example, on an FRSM12 connection where mir-based derivation does not apply, frConnMCR defaults to the same value already computed for frConnPCR rather than to a separately derived minimum rate.