80C188EB EXAMPLE INTERFACE
Because the 80186/80188 microprocessors are designed as embedded controllers, this section of the text provides an example of such an application. The example illustrates simple memory and I/O attached to the 80C188EB microprocessor. It also lists the software required to program the 80C188EB and its internal registers after a system reset. Figure 16–24 illustrates the pin-out of the 80C188EB version of the 80188 microprocessor. Notice the differences between this version and the XL version presented earlier in the text.
The 80C188EB version contains some new features that were not present on earlier versions. These features include two I/O ports (P1 and P2) that are shared with other functions and two serial communications interfaces that are built into the processor. This version does not contain a DMA controller, as did the XL version.
The 80188EB can be interfaced with a small system designed to be used as a microprocessor trainer. The trainer illustrated in this text uses a 27256 EPROM for program storage, a 62256 SRAM for data storage, and an 8255 for a keyboard and LCD display interface. Figure 16–25 illustrates a small microprocessor trainer that is based on the 80C188EB microprocessor.
Memory is selected by the UCS pin for the 27C256 EPROM and the LCS pin for the 62256 SRAM; the GCS0 pin selects the 8255. The system software places the EPROM at memory addresses F8000H–FFFFFH; the SRAM at 00000H–07FFFH; and the 8255 at I/O ports 0000H–003FH (software uses ports 0, 1, 2, and 3). In this system, as is normally the case, we do not modify the address of the peripheral control block, which resides at I/O ports FF00H–FFFFH. Example 16–5 lists the software required to initialize the 80C188EB microprocessor. This example completely programs the 80C188EB and also the entire system. The software is discussed in the next section of this chapter.
