{"id":139,"date":"2025-03-04T17:59:17","date_gmt":"2025-03-04T16:59:17","guid":{"rendered":"https:\/\/abc80.dk\/?page_id=139"},"modified":"2025-03-16T22:05:49","modified_gmt":"2025-03-16T21:05:49","slug":"circuit-explanation","status":"publish","type":"page","link":"https:\/\/abc80.dk\/?page_id=139","title":{"rendered":"Circuit explanation"},"content":{"rendered":"\n
\n
Power supplies <\/a><\/div>\n\n\n\n
Video<\/a><\/div>\n<\/div>\n\n\n\n

<\/p>\n\n\n\n

Block diagram<\/strong><\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n


Z80 PIO Parallel Input\/Output<\/strong><\/p>\n\n\n\n

The PIO handles the Keyboard, the tape drive and the V24 (RS232} serial port.<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

<\/p>\n\n\n\n

12 MHz X-Tal clock<\/h2>\n\n\n\n

A crystal of approx 12 MHz is divided down to approx 3 MHz for the Z80A CPU. It is also divided to other purposes.<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

<\/p>\n\n\n\n

54LS166 Parallel to serial register <\/h2>\n\n\n\n

Located in the video block<\/p>\n\n\n\n

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.<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

<\/p>\n\n\n\n

Dynamic RAM, 16 kbyte for software programs<\/h2>\n\n\n\n

Located in the 16 K RAM block. <\/p>\n\n\n\n

The dynamic RAM is not just powered by 5V. It also requires 12V and -5V in order to work and remember values. <\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

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..<\/p>\n\n\n\n

The RAM needs to be refreshed every 2 ms to keep the data.<\/p>\n\n\n\n

Static RAM 1 KByte for video memory<\/h2>\n\n\n\n

Located in the video block<\/p>\n\n\n\n

The video is 40 characters in 24 lines = 960 bytes.<\/p>\n\n\n\n

The two TMS4045 IC’s D1 and C1 are each 4 bit memory with 1K Static RAM that does not need to be refreshed.<\/p>\n\n\n\n

ROM 16 kbyte for Basic interpreter and operating system.<\/h2>\n\n\n\n

TMS4732 is an 4 Kbyte 8 bit ROM IC. They have the dedignatorscA2, A3, A4, and A5 giving 16 Kbyte ROM in total <\/p>\n\n\n\n

<\/span>\"\"
\n

<\/p>\n<\/div><\/div>\n\n\n\n

SN76477 Sound generator<\/h2>\n\n\n\n

Located in the Sound block and the output goes to the monitor and to the casette Tape station.<\/p>\n\n\n\n

So expect that whenever software should be saved on tape the noise will be heard in the speaker of the monitor.<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

The sound IC does not have a Address\/data bus but a latch will let the Z80A control the needed pins <\/p>\n","protected":false},"excerpt":{"rendered":"

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 […]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-139","page","type-page","status-publish","hentry"],"yoast_head":"\nCircuit explanation - Luxor ABC 80<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/abc80.dk\/?page_id=139\" \/>\n<meta property=\"og:locale\" content=\"da_DK\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Circuit explanation - Luxor ABC 80\" \/>\n<meta property=\"og:description\" content=\"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. 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