Yamaha dx7/9 manual Main CPU Operation, Ram, Rom, Led

4-6. Data is not accepted from the panel switches and keys while the sub-CPU C2 line is low.

5.Main CPU Operation

The main CPU mode is set by externally initializing lines P20~P22. When “L, L, H” is applied to the P20~P22 lines and latched into the CPU on the rising edge of RES, the Extended Multiplex Mode is selected.

In this mode, P40 ~ P47 function as address lines. The lower address bits are multiplexed with the data on lines P30 ~ P37, and are separated by the address strobe signal SCI.

P20 ~ P24 and P10 ~ P17 function as I/O lines.

6.RAM

M5M511BP-15 X 8-bit CMOS RAM.

7.ROM

2764 8K X 8-bit NMOS EROM

8.LED

The LED display is created via software. The LEDs are lit by data latched from the

main CPU.