The XRT86SH328 has a total of 42 independent E1 framers (or 56 independent framers for T1). This Voyager Device maps 21 E1 payloads up to STS-3/ STM-1. The purpose of the 42 framers is to allow back-to-back transmit and receive framers on each of the 21 channel Egress and Ingress data paths. The channel numbering system references the framers according to the block diagram shown in Figure 1, where every 4TH Channel is not used in E1 mode. The XRT86SH328 provides E1 framing and error accumulation in accordance with ANSI/ITU_T specifications. Each framer has its own framing synchronizer and transmit-receive slip buffers. The slip buffers can be independently enabled or disabled as required and can be configured to frame to the common E1 signal formats.