Level 20: Dual Read
Task
Add a second ROM for reading 2-byte operands. PC steps by +2.
In word format, each instruction takes 2 bytes. The first ROM holds opcodes, the second ROM holds operands.
Solution
Both ROMs are addressed by PC (which steps by +2). This means: - ROM[0] outputs the opcode (high byte of instruction), - ROM#1 (second ROM) outputs the operand (low byte).
Tasks: 1. BusConstant = 2 → PC Inc input (same as level 19). 2. ROM#1.Q → RAM Addr input. This routes the instruction operand to the RAM address input — now LDA/STA will work with 8-bit addresses.
Tip: ROM#1 (second ROM) is located below the first ROM on the canvas. Its output pin is labeled Q.