4.2.2Addressing a Location Through a Window

8XC196Kx, Jx, CA USER’S MANUAL

Appendix C includes a table of the windowable SFRs with the WSR values and windowed direct addresses for each window size. Examples beginning on page 4-20 explain how to determine the WSR value and windowed direct address for any windowable location. An additional example shows how to set up a window by using the linker locator.

Table 4-11. Windows

NOTE: Locations 1FE0–1FFFH cannot be windowed. Reading these locations through a window returns FFH; writing these locations through a window has no effect.

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NOTE: Locations 1FE0–1FFFH cannot be windowed. Reading these locations through a window returns FFH; writing these locations through a window has no effect.

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8XC196Kx, Jx, CA USER’S MANUAL

Table 4-12. Windowed Base Addresses

Appendix C includes a table of the windowable SFRs with the WSR values and direct addresses for each window size. The following examples explain how to determine the WSR value and direct address for any windowable location. An additional example shows how to set up a window by using the linker locator.

4.2.2.132-byte Windowing Example

Assume that you wish to access location 014BH (a location in the upper register file used for gen- eral-purpose register RAM) with register-direct addressing through a 32-byte window. Table 4-11 on page 4-18 shows that you need to write 4AH to the window selection register. It also shows that the base address of the 32-byte memory area is 0140H. To determine the offset, subtract that base address from the address to be accessed (014BH – 0140H = 000BH). Add the of fset to the base address of the window in the lower register file (00E0H, from Table 4-12). The direct address is 00EBH (000BH + 00E0H)

4.2.2.264-byte Windowing Example

Assume that you wish to access the COMP1_CON register (location 1F8CH) with register-direct addressing through a 64-byte window. Table 4-11 on page 4-18 shows that you need to write 3EH to the window selection register. It also shows that the base address of the 64-byte memory area is 1F80H. To determine the offset, subtract that base address from the address to be accessed (1F8CH – 1F80H = 000C H). Add the offset to the base address of the window in the lower register file (00C0H, from Table 4-12). The direct address is 00CCH (000CH + 00C0H).

4.2.2.3128-byte Windowing Example

Assume that you wish to access location 1F82H (the EPA8_TIME register) with register-direct addressing through a 128-byte window. Table 4-11 on page 4-18 shows that you need to write 1FH to the window selection register. It also shows that the base address of the 128-byte memory area is 1F80H. To determine the offset, subtract that base address from the address to be accessed (1F82H – 1F80H = 0002H). Add the offset to the base address of the window in the lower register file (0080H, from Table 4-12). The direct address is 0082H (0002H + 0080H).

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