Intel 80C188XL, 80C186XL Chapter Peripheral Control Block, 4.1PERIPHERAL CONTROL REGISTERS

CHAPTER 4

PERIPHERAL CONTROL BLOCK

All integrated peripherals in the 80C186 Modular Core family are controlled by sets of registers within an integrated Peripheral Control Block (PCB). The peripheral control registers are physi- cally located in the peripheral devices they control, but they are addressed as a single block of registers. The Peripheral Control Block encompasses 256 contiguous bytes and can be located on any 256-byte boundary of memory or I/O space. The PCB Relocation Register, which is also lo- cated within the Peripheral Control Block, controls the location of the PCB.

4.1PERIPHERAL CONTROL REGISTERS

Each of the integrated peripherals’ control and status registers is located at a fixed offset above the programmed base location of the Peripheral Control Block (see Table 4-1). These registers are described in the chapters that cover the associated peripheral. “Accessing the Peripheral Con- trol Block” on page 4-4 discusses how the registers are accessed and outlines considerations for reading and writing them.

4.2PCB RELOCATION REGISTER

In addition to control registers for the integrated peripherals, the Peripheral Control Block con- tains the PCB Relocation Register (Figure 4-1). The Relocation Register is located at a fixed off- set within the Peripheral Control Block (Table 4-1). If the Peripheral Control Block is moved, the Relocation Register also moves.

The PCB Relocation Register allows the Peripheral Control Block to be relocated to any 256-byte boundary within memory or I/O space. The Memory I/O bit (MEM) selects either memory space or I/O space, and the R19:8 bits specify the starting (base) address of the PCB. The remaining bit, Escape Trap (ET), controls access to the math coprocessor interface.

“Setting the PCB Base Location” on page 4-6 describes how to set the base location and outlines some restrictions on the Peripheral Control Block location.

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