ACC HDLC-NRM (SDLC) User's Guide

Protocol Specific Configuration
Protocol Configuration Values
Chapter 456
NOTE Use of the TWS option is not recommended when there are multiple
polled primary terminals configured on the line (i.e. multipoint rather
than point-to-point). This is for the reason that, when a secondary
terminal has high volumes of data to send, the primary station keeps
acknowledging received frames, consequently allowing the secondary an
arbitrarily long time to return the final bit to the poll. Since in the TWS
mode the interval between polls is indeterminate, using the TWS option
under these conditions is not recommended.
SEC - Secondary Station
Set to make the terminal a secondary station. If this option flag is set to
zero (0), then this terminal is configured as a primary station. Primary
and Secondary terminals cannot be mixed on a single port.