NEO-ZMC
Z80 memory controller. Has a hardwired 32KiB bank and switchable 16/8/4/2KiB banks arranged as a register file. To save pins the high address lines (A15-A8) are used for data input. The chip's write strobe is (port) address decoded inside the console.
Pinout
OpenOffice Draw file: File:Neo-zmc.odg
Operation
SDA10,SDA9,SDA8 are the bank selector and SDA1,SDA0 is the bank size selector
SDA1,SDA0 = 0,0 select bank ranges of 2Kbytes (64k M1)
SDA1,SDA0 = 0,1 select bank ranges of 4Kbytes (128k M1)
SDA1,SDA0 = 1,0 select bank ranges of 8Kbytes (256k M1)
SDA1,SDA0 = 1,1 select bank ranges of 16Kbytes (512k M1)
SDRD0 is the memory operation selector WRITE (set bank and range size) / READ (access M1 based in previous configuration)
Details:
We must put SDRD0 is in high logic level before configure any bank;
To configure a bank to be accessed (e.g. bank0):
Set SDRD0 from H to L (prepare for new bank configuration, let output in tri-state and accept inputs)
Set SDA[15..0] = $8003 (select bank 0 and 16k range size)
Set SDRD0 from L to H (fix bank, and ready to convert inputs in proper outputs signals)
With SDRD0 in H, send inputs SDA[15..0] from $8000~BFFF, ZMC will convert this range in M1 range from $00000~$03FFF;
Set SDRD0 from H to L (prepare for new bank configuration, let output in tri-state and accept inputs)
Set SDA[15..0] = $8103 (select bank 0 and 16k range size)
Set SDRD0 from L to H (fix bank, and ready to convert inputs in proper outputs signals)
With SDRD0 in H, send inputs SDA[15..0] from $8000~BFFF, ZMC will convert this range in M1 range from $04000~$07FFF;
Set SDRD0 from H to L (prepare for new bank configuration, let output in tri-state and accept inputs)
Set SDA[15..0] = $8203 (select bank 0 and 16k range size)
Set SDRD0 from L to H (fix bank, and ready to convert inputs in proper outputs signals)
With SDRD0 in H, send inputs SDA[15..0] from $8000~BFFF, ZMC will convert this range in M1 range from $08000~$0BFFF;
Set SDRD0 from H to L (prepare for new bank configuration, let output in tri-state and accept inputs)
Set SDA[15..0] = $8303 (select bank 0 and 16k range size)
Set SDRD0 from L to H (fix bank, and ready to convert inputs in proper outputs signals)
With SDRD0 in H, send inputs SDA[15..0] from $8000~BFFF, ZMC will convert this range in M1 range from $0C000~$0FFFF;
... and so on...
| Here is the table for the banks of 512k rom |
|---|
| 8003 => bank 00 (acess 00000‐03FFF ) |
| 8103 => bank 01 (acess 04000‐07FFF ) |
| 8203 => bank 02 (acess 08000‐0BFFF ) |
| 8303 => bank 03 (acess 0C000‐0FFFF ) |
| 8403 => bank 04 (acess 10000‐13FFF ) |
| 8503 => bank 05 (acess 14000‐17FFF ) |
| 8603 => bank 06 (acess 18000‐1BFFF ) |
| 8703 => bank 07 (acess 1C000‐1FFFF ) |
| 8803 => bank 08 (acess 20000‐23FFF ) |
| 8903 => bank 09 (acess 24000‐27FFF ) |
| 8A03 => bank 10 (acess 28000‐2BFFF ) |
| 8B03 => bank 11 (acess 2C000‐2FFFF ) |
| 8C03 => bank 12 (acess 30000‐33FFF ) |
| 8D03 => bank 13 (acess 34000‐37FFF ) |
| 8E03 => bank 14 (acess 38000‐3BFFF ) |
| 8F03 => bank 15 (acess 3C000‐3FFFF ) |
| 9003 => bank 16 (acess 40000‐43FFF ) |
| 9103 => bank 17 (acess 40000‐47FFF ) |
| 9203 => bank 18 (acess 40000‐4BFFF ) |
| 9303 => bank 19 (acess 40000‐4FFFF ) |
| 9403 => bank 20 (acess 50000‐53FFF ) |
| 9503 => bank 21 (acess 54000‐57FFF ) |
| 9603 => bank 22 (acess 58000‐5BFFF ) |
| 9703 => bank 23 (acess 5C000‐5FFFF ) |
| 9803 => bank 24 (acess 60000‐63FFF ) |
| 9903 => bank 25 (acess 64000‐67FFF ) |
| 9A03 => bank 26 (acess 68000‐6BFFF ) |
| 9B03 => bank 27 (acess 6C000‐6FFFF ) |
| 9C03 => bank 28 (acess 70000‐73FFF ) |
| 9D03 => bank 29 (acess 74000‐77FFF ) |
| 9E03 => bank 30 (acess 78000‐7BFFF ) |
| 9F03 => bank 31 (acess 7C000‐7FFFF ) |