IA88C00-PDW48I-R datasheet(16/80 Pages) INNOVASIC

16 / 80 page

IA88C00

Data Sheet

Microcontroller

As of Production Version -01

ENG 21 0 050519-00

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Innovasic Semiconductor

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High order bit of the 4-bit address selects one of the two register pointers (0 selects RP0; 1 selects RP1).

Live high order bits in the register pointer select an 8-register (contiguous) slice of the register space.

Three low order bits of the 4-bit address select one of the eight registers in the slice.

The process results in linking together the five bits from the register pointer to the three bits from the

address to form an 8-bit address. The three bits from the address will always point to an address within

the same eight registers, as long as the address in the register pointer remains unchanged.

Changing the five high bits in control registers R214 for RP9 and R215 for RP1 allows the register

pointers to be moved.

Using full 8-bit addressing allows the working registers to be accessed. The lower nibble is used similarly

to the 4-bit addressing described above when an 8-bit logical address in the range 192 to 207 (C0 to CF)

is specified. This is shown in section b. of Figure 8.

Together They Create 8-Bit Register Address

Selects RP0

or RP1

RP0 (R214)

RP1 (R215)

Address

Opcode

Five High-Order Bits

4-Bit Address Provides Three Low-Order Bits

a. 4-Bit Addressing

Selects RP0

or RP1

RP0 (R214)

RP1 (R215)

Address

Five High-Order Bits

b. 8-Bit Addressing

8-Bit Physical Address

8-Bit

Logical

Address

Three Low-

Order Bits

Figure 8. Working Register Window

Physical registers 192 to 207 can be accessed only when selected by a register pointer. This is because

any direct access to logical addresses 192 to 207 involves the register pointers. After a reset, RP0 points

to R192 and RP1 points to R200.

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