SECTION 2 - INTRODUCTION
The SGS - Thomson SS7 Signalling Link Controller (MK50H27) is a VLSI semiconductor device which provides a complete level 2 data communication control conforming to the CCITT, ANSI, BELLCORE, and AT&T versions of SS7, as well as options to allow conformance to TTC JT-Q703 (Japanese SS7). This includes signal unit formatting, transparency (so-called "bit-stuffing"), error recovery by two types of retransmission, error monitoring, sequence number control, link status control, and fill in signal unit generation.

SECTION 1 - FEATURES
■ Complete Level 2 Implementation of SS7.
■ Compatible with 1988 CCITT, AT&T, ANSI, and Bellcore Signalling System Number 7 link level protocols.
■ Optional operation to comply with Japanese TTC JT-Q703 specification requirements
■ Pin-for-pin and architecturally compatible with MK50H25 (X.25/LAPD), MK50H29 (SDLC), and MK50H28(Frame Relay).
■ System clock rates up to 33 MHz (MK50H27 - 33), or 25 MHz (MK50H27 - 25).
■ Data rate up to 4 Mbps continuous for SS7 protocol processing, 20 Mbps for transparent HDLC mode, or up to 51 Mbps bursted (gapped data clocks, non-continuous data).
■ On chip DMA control with programmable burst length.
■ DMA transfer rate of up to 13.3 Mbytes/sec using optional 5 SYSCLK DMA cycle (150 nS) at 33 MHz SYSCLK.
■ Buffer Management includes:
    - Initialization Block
    - Separate Receive and Transmit Rings
    - Variable Descriptor Ring and Window Sizes.
■ Selectable BEC or PCR retransmission methods, including forced retransmission for PCR.
■ Handles all 7 SS7 Timers, plus the additional
■ Signal Unit interval timers for Japanese SS7.
■ Handles all SS7 frame formatting:
    - Zero bit insert and delete
    - FCS generation and detection
    - Frame delimiting with flags
■ Programmable minimum Signal Unit spacing (number of flags between SU’s)
■ Handles all sequencing and link control.
■ Selectable FCS of 16 or 32 bits.
■ Testing Facilities:
    - Internal Loopback
    - Silent Loopback
    - Optional Internal Data Clock Generation
    - Self Test.
■ Programmable for full or half duplex operation Programmable Watchdog Timers for RCLK and TCLK (to detect absence of data clocks)