Initial Register Values; Data Formats - Hitachi H8/3637 Hardware Manual

2.2.3

Initial Register Values

When the CPU is reset, the program counter (PC) is initialized to the value stored at address
H'0000 in the vector table, and the I bit in the CCR is set to 1. The other CCR bits and the general
registers are not initialized. In particular, the stack pointer (R7) is not initialized. R7 initialization
should therefore be carried out immediately after a reset.
2.3

Data Formats

The H8/300L CPU can process 1-bit data, 4-bit (BCD) data, 8-bit (byte) data, and 16-bit (word)
data.
Bit manipulation instructions operate on 1-bit data specified as bit n in a byte operand
(n = 0, 1, 2, ..., 7).
All arithmetic and logic instructions except ADDS and SUBS can operate on byte data.
The MOV.W, ADD.W, SUB.W, CMP.W, ADDS, SUBS, MULXU (8 bits × 8 bits), and DIVXU
(16 bits ÷ 8 bits) instructions operate on word data.
The DAA and DAS instructions perform decimal arithmetic adjustments on byte data in two-digit
4-bit BCD form.
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