The Philips Semiconductors SCC2698B Octal UART is composed of four blocks, each logically equivalent to a 2681 or 2692 DUART. Each block is composed of two channels, a counter/timer, and an interrupt control section. The channels are matched to the blocks as shown in Figure 1. The blocks are indicated by capital letters A, B, C, and D; the channels are indicated by lower-case letters a, b, c, d, e, f, g, and h. All registers act either on a block or an individual channel.