NEO-ZMC

NEO-ZMC chip on a MVS cartridge. Picture courtesy of [MVS-Scans].

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

File:Neo-zmc pinout.png

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 1 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 2 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 3 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...

DWORD (SDA[15..0])	BANK	RANGE (M1 A[18..0])
$8003	bank 00	$00000~$03FFF
$8103	bank 01	$04000~$07FFF
$8203	bank 02	$08000~$0BFFF
$8303	bank 03	$0C000~$0FFFF
$8403	bank 04	$10000~$13FFF
$8503	bank 05	$14000~$17FFF
$8603	bank 06	$18000~$1BFFF
$8703	bank 07	$1C000~$1FFFF
$8803	bank 08	$20000~$23FFF
$8903	bank 09	$24000~$27FFF
$8A03	bank 10	$28000~$2BFFF
$8B03	bank 11	$2C000~$2FFFF
$8C03	bank 12	$30000~$33FFF
$8D03	bank 13	$34000~$37FFF
$8E03	bank 14	$38000~$3BFFF
$8F03	bank 15	$3C000~$3FFFF
$9003	bank 16	$40000~$43FFF
$9103	bank 17	$40000~$47FFF
$9203	bank 18	$40000~$4BFFF
$9303	bank 19	$40000~$4FFFF
$9403	bank 20	$50000~$53FFF
$9503	bank 21	$54000~$57FFF
$9603	bank 22	$58000~$5BFFF
$9703	bank 23	$5C000~$5FFFF
$9803	bank 24	$60000~$63FFF
$9903	bank 25	$64000~$67FFF
$9A03	bank 26	$68000~$6BFFF
$9B03	bank 27	$6C000~$6FFFF
$9C03	bank 28	$70000~$73FFF
$9D03	bank 29	$74000~$77FFF
$9E03	bank 30	$78000~$7BFFF
$9F03	bank 31	$7C000~$7FFFF