Block diagram
Z80 PIO Parallel Input/Output
The PIO handles the Keyboard, the tape drive and the V24 (RS232} serial port.
12 MHz X-Tal clock
A crystal of approx 12 MHz is divided down to approx 3 MHz for the Z80A CPU. It is also divided to other purposes.
54LS166 Parallel to serial register
Located in the video block
The 54LS166 (J1) is a 8 bit parallel load input to 1 bit output that clocks the inputs from the character generator out for Video signal.
Dynamic RAM, 16 kbyte for software programs
Located in the 16 K RAM block.
The dynamic RAM is not just powered by 5V. It also requires 12V and -5V in order to work and remember values.
The TMS 4116 is a 1 bit 16 kbit Dynamic RAM IC. 8 of these ic’s give 16 kbyte memory for the Z80A processor..
The RAM needs to be refreshed every 2 ms to keep the data.
Static RAM 1 KByte for video memory
Located in the video block
The video is 40 characters in 24 lines = 960 bytes.
The two TMS4045 IC’s D1 and C1 are each 4 bit memory with 1K Static RAM that does not need to be refreshed.
ROM 16 kbyte for Basic interpreter and operating system.
TMS4732 is an 4 Kbyte 8 bit ROM IC. They have the dedignatorscA2, A3, A4, and A5 giving 16 Kbyte ROM in total
SN76477 Sound generator
Located in the Sound block and the output goes to the monitor and to the casette Tape station.
So expect that whenever software should be saved on tape the noise will be heard in the speaker of the monitor.
The sound IC does not have a Address/data bus but a latch will let the Z80A control the needed pins