59 lines
3.3 KiB
Plaintext
59 lines
3.3 KiB
Plaintext
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_______________________________________________________________________________
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Expansion of the Z80 CPU Chip
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Written by King Lucifer (Alias Byteman) on 9/10/88
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A Telecom Computer Security Bulletin File
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Volume One, Number 1, File 12 of 12
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The circut described here expands the z80 uP's 64k byte memory space to
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512k bytes by switching among sixteen 32k byte banks. The approach allows
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you to programs larger than 64k bytes for applications that can tolerate
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an I/O operation each time the program crosses one of the 32k byte -
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boundaries.
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The Z80's lower address lines (Schematic) provide access to the 32k-byte
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common bank of memory. The sixteenth line (A15 through A18) by activating
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four additional bits (A15 through A18) Consequently, the system can access
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2;19 or 512k, unique memory locations.
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Schematic
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---------
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_____________________________________________> (Ao - A14)
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________ / \ __________
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| z80 ao|_/ \|a ic 0|o________
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| ic1 a1|_| |_|b 74ls1381|o--o |
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| |_| |_|c 2|o--o |
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| .|_| | | 3|o--o |
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| .|_| _____|en 4|o--o |
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| .|_| | ___|en 5|o--o |
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| |_| | | _|en 6:o--o |
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| |_| | | | | 7:o--o |___ ______ _______
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| |_| | | - | | | | | |
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| |_| | | |__________| ____|d Q|____| - |
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| |_| | | |____|d Q|____| | |
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| |___________|_|_____ |____|d Q|____| | A |
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| |___ | | | | | 74ls | | - |
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| |___| | | | | ~~~~|~~~ | -|a1
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| |___| | | | | O | | |a2
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| |___| | | | | | | | |a3
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| |___| | | | | | | | |a4
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| Z80 |___| | | | | | | -|
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| |___| | | | | | | - |
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| |___| | | | | | __| | |
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| | | | | | | | |__| |B |
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|________| | | | | | | |__| | |
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O O | | | | | | |__| - |
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| |______________| | | | | | |_______|
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|_____________________| | | | | O |
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|| | | | | |____| |
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|| |_______________|_________________/_________|____________|_do-7
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|| o(5v) |______________--- _________|____________|
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|| |_____--- ___________________/---
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||_________________/---
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o________________________________________________________|
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ln
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_______________________________________________________________________________
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$ |