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