Multiply-Accumulate Register (Mac); Initial Values Of Cpu Registers; 2Data Formats; General Register Data Formats - Renesas H8SX/1520 Series Hardware Manual

2.5.7

Multiply-Accumulate Register (MAC)

MAC is a 64-bit register that stores the results of multiply-and-accumulate operations. It consists
of two 32-bit registers denoted MACH and MACL. The lower 10 bits of MACH are valid; the
upper bits are sign extended. The MAC contents are changed with the MAC, CLRMAC, LDMAC,
and STMAC instructions.
2.5.8

Initial Values of CPU Registers

Reset exception handling loads the start address from the vector table into the PC, clears the T bit
in EXR to 0, and sets the I bits in CCR and EXR to 1. The general registers, MAC, and the other
bits in CCR are not initialized. In particular, the initial value of the stack pointer (ER7) is
undefined. The SP should therefore be initialized using an MOV.L instruction executed
immediately after a reset.
2.6

2Data Formats

The H8SX 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.
2.6.1

General Register Data Formats

Figure 2.12 shows the data formats in general registers.
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REJ09B0104-0300
Section 2 CPU