NEO-BUF: Difference between revisions

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[[File:cd2_buf.jpg|right|thumb|NEO-BUF chip used to split DRAM access on a CDM3-2 board.]]
{{ChipInfo
|picture=cd2_buf.jpg
|pkg=QFP48
|manu=fujitsu
|date=1994 ?
|gates=
|used_on={{PCB|MV1A}} {{PCB|MV1B}} {{PCB|NEO-CDM3-2_board}}
}}


Dual 8 bit bus switch.
Dual 74HC245 octal transceivers in one chip.
This chip is extensively used in [[CD systems]] to multiplex subsystem and {{Chipname|68k}} accesses to [[DRAM]]s.


[[File:Neo-bufpinout1.png]]
Also found on late [[MVS hardware|MVS]] boards.


Putting the CTRL lines high make the corresponding bus pass through the chip.
==Pinout==
Setting it low makes the output hi-Z. This chip is extensively used in the NeoGeo CD to switch in between [[DRAM]]s (both output buses are tied together to a common one, and go to the [[NEO-GRC]] or [[NEO-GRZ]] chips).


[[Catégorie:Chips]]
{{Pinout|NEO-BUF|512px}}
 
==Replacement==
[[File:Neo-buf_bypass.jpg|thumb|Picture from MVS-Scans]]
On some MVS boards, some NEO-BUF chips are just used as buffers for the [[68k]] data bus. There are reports of succesful repairs done by replacing them with a small bypass board which simply connects the A side with the B side (see picture).
 
Note that this should '''NOT''' be done to replace damaged NEO-BUF chips which are used for other purposes. This can only work for:
* GA1 on the SLOT1B board of the {{PCB|MV1B}}
* GA11 on the {{PCB|MV1A}}
 
[[Category:Chips]]
[[Category:Repairs]]

Revision as of 01:39, 8 July 2018

Package QFP48
Manufacturer
First use 1994 ?
Used on MV1A MV1B NEO-CDM3-2_board

Dual 74HC245 octal transceivers in one chip. This chip is extensively used in CD systems to multiplex subsystem and 68k accesses to DRAMs.

Also found on late MVS boards.

Pinout


Edit this pinout

Replacement

Picture from MVS-Scans

On some MVS boards, some NEO-BUF chips are just used as buffers for the 68k data bus. There are reports of succesful repairs done by replacing them with a small bypass board which simply connects the A side with the B side (see picture).

Note that this should NOT be done to replace damaged NEO-BUF chips which are used for other purposes. This can only work for:

  • GA1 on the SLOT1B board of the MV1B
  • GA11 on the MV1A