W921E840A Datasheet, PDF (47/58 Pages) Winbond – 4-BIT MICROCONTROLLER

W921E840A/W921C840
9. ADDRESSING MODE
There are ROM, RAM, and Look-up table addressing modes in this chip.
9.1 ROM Addressing Mode
There are two types of ROM addressing mode in this chip:
• Indirect call addressing mode (0000H to 0FFFH)
• Long call/jump addressing mode (0000H to 1FFFH)
9.1.1 Indirect Call Addressing Mode: (1 word/2 cycles)
ROM CODE b9 b8 b7 b6 b5 b4 b3 b2 b1 b0 ^{b3 b2 b1 b0} b3 b2 b1 b0
decoder code
i3 i2 i1 i0
B Register A Register
Instruction: CALLP
PC b12 b11 b10 b9 b8 b7 b6 b5 b4 b3 b2 b1 b0
0 i3 i2 i1 i0 b3 b2 b1 b0 a3 a2 a1 a0
9.1.2 Long Call/Jump Addressing Mode: (2 words/2 cycles)
ROM CODE b9 b8 b7 b6 b5 b4 b3 b2 b1 b0
decoder code
b9 b8 b7 b6 b5 b4 b3 b2 b1 b0
PC
b12 b11 b10 b9 b8 b7 b6 b5 b4 b3 b2 b1 b0
Instruction: CALL, JMPL, JB0, JB1, JB2, JB3, JC, JNC, JZ, JNZ
9.2 RAM Addressing Mode
There are three types of RAM addressing mode in this chip:
• Direct addressing mode
• Indirect addressing mode
• Working register addressing mode
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Publication Release Date: July 1999
Revision A3