H8SSLASH2218 datasheet(91/750 Pages) RENESAS

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Section 2 CPU

Rev.6.00 Jun. 03, 2008 Page 43 of 698

REJ09B0074-0600

Bit

Bit Name

Initial Value

R/W Description

undefined

R/W Overflow Flag

Set to 1 when an arithmetic overflow occurs, and cleared to

0 at other times.

undefined

R/W Carry Flag

Set to 1 when a carry occurs, and cleared to 0 otherwise.

Used by:

• Add instructions, to indicate a carry

• Subtract instructions, to indicate a carry

• Shift and rotate instructions, to indicate a carry

They carry flag is also used as a bit accumulator by bit

manipulation instructions.

2.4.5

Initial Register Values

Reset exception handling loads the CPU's program counter (PC) from the vector table, clears the

trace bit in EXR to 0, and sets the interrupt mask bits in CCR and EXR to 1. The other CCR bits

and the general registers are not initialized. In particular, the stack pointer (ER7) is not initialized.

The stack pointer should therefore be initialized by an MOV.L instruction executed immediately

after a reset.

2.5

Data Formats

The H8S/2000 CPU can process 1-bit, 4-bit (BCD), 8-bit (byte), 16-bit (word), and 32-bit

(longword) data. Bit-manipulation instructions operate on 1-bit data by accessing bit n (n = 0, 1, 2,

…, 7) of byte operand data. The DAA and DAS decimal-adjust instructions treat byte data as two

digits of 4-bit BCD data.

2.5.1

General Register Data Formats

Figure 2.9 shows the data formats in general registers.

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