HD6432670 Hitachi, HD6432670 Datasheet - Page 97

• Manufacturer Part Number: HD6432670
• Description: (HD64F267x Series) 16-Bit Microcomputer
• Manufacturer: Hitachi

2.7.7
This mode is used in the Bcc and BSR instructions. An 8-bit or 16-bit displacement contained in
the instruction code is sign-extended and added to the 24-bit PC contents to generate a branch
address. Only the lower 24 bits of this branch address are valid; the upper 8 bits are all assumed to
be 0 (H'00). The PC value to which the displacement is added is the address of the first byte of the
next instruction, so the possible branching range is –126 to +128 bytes (–63 to +64 words) or –
32766 to +32768 bytes (–16383 to +16384 words) from the branch instruction. The resulting value
should be an even number.
2.7.8
This mode can be used by the JMP and JSR instructions. The instruction code contains an 8-bit
absolute address specifying a memory operand. This memory operand contains a branch address.
The upper bits of the absolute address are all assumed to be 0, so the address range is 0 to 255
(H'0000 to H'00FF in normal mode, H'000000 to H'0000FF in advanced mode).
In normal mode the memory operand is a word operand and the branch address is 16 bits long. In
advanced mode the memory operand is a longword operand, the first byte of which is assumed to
be all 0 (H'00). Note that the first part of the address range is also the exception vector area. For
further details, refer to section 4, Exception Handling.
If an odd address is specified in word or longword memory access, or as a branch address, the
least significant bit is regarded as 0, causing data to be accessed or instruction code to be fetched
at the address preceding the specified address. (For further information, see section 2.5.2, Memory
Data Formats.)
Note: Normal mode is not available in this LSI.
Program-Counter Relative—@(d:8, PC) or @(d:16, PC)
Memory Indirect—@@aa:8
Specified
by @aa:8
Figure 2.12 Branch Address Specification in Memory Indirect Mode
Note: * Normal mode is not available in this LSI.
(a) Normal Mode
Branch address
*
Specified
by @aa:8
(a) Advanced Mode
Rev. 2.0, 04/02, page 51 of 906
Branch address
Reserved