Revision as of 22:58, 27 January 2012

This chip is used in cartridges to replace 74LS273 and 74LS174 latches that were used in early boards (Like on CHA-32).

It includes one 16-bit latch (to address a 128KiB S ROM) and one 20-bit latch (to address 8MiB of C ROMs) in one package. Note that A4 of the C ROMs and A3 of the S ROM are not part of the multiplexed bus and come straight from the cartridge edge, bypassing this chip.

It was later replaced by NEO-CMC which performs the same function along with quite a few other things.

For cartridges that use this chip but have more than 8MiB of C ROM, extra bits were added using 7400 chips. An added LS74 (2 bits) in CHA256 boards for example increases the C ROM capacity from 8MiB to 32MiB (256M).

Demultiplexing

P BUS	P19	P18	P17	P16	P15	P14	P13	P12	P11	P10	P9	P8	P7	P6	P5	P4	P3	P2	P1	P0
C address	A3	A2	A1	A0	A20	A19	A18	A17	A16	A15	A14	A13	A12	A11	A10	A9	A8	A7	A6	A5
S address					A4	A2	A1	A0	A16	A15	A14	A13	A12	A11	A10	A9	A8	A7	A6	A5

Pinout

File:Neo-273 pinout.png

OpenOffice Draw file: File:Neo-273.odg

@@ Line 1: / Line 1: @@
 [[File:crt_273.jpg|right|thumb|NEO-273 chip in a MVS [[cartridges|cartridge]]. Picture courtesy of [[http://www.mvs-scans.com MVS-Scans]].]]
-One 16-bit D-FF (to address a 128KiB [[S ROM]]) and one 20-bit D-FF (to address 8MiB of [[C ROM]]s) in one package. Later replaced by the [[NEO-CMC]] which performs the same function along with quite a few other things.
+This chip is used in cartridges to replace 74LS273 and 74LS174 latches that were used in early boards (Like on [[CHA board|CHA-32]]).
+It includes one 16-bit latch (to address a 128KiB [[S ROM]]) and one 20-bit latch (to address 8MiB of [[C ROM]]s) in one package. Note that A4 of the C ROMs and A3 of the S ROM are not part of the multiplexed bus and come straight from the cartridge edge, bypassing this chip.
+It was later replaced by [[NEO-CMC]] which performs the same function along with quite a few other things.
 For cartridges that use this chip but have more than 8MiB of C ROM, extra bits were added using 7400 chips. An added LS74 (2 bits) in CHA256 boards for example increases the C ROM capacity from 8MiB to 32MiB (256M).
+==Demultiplexing==
+{|class="wikitable"
+!P BUS||P19||P18||P17||P16||P15||P14||P13||P12||P11||P10||P9||P8||P7||P6||P5||P4||P3||P2||P1||P0
+|-
+|C address||A3||A2||A1||A0||A20||A19||A18||A17||A16||A15||A14||A13||A12||A11||A10||A9||A8||A7||A6||A5
+|-
+|S address|| || || || ||A4||A2||A1||A0||A16||A15||A14||A13||A12||A11||A10||A9||A8||A7||A6||A5
+|}
 =Pinout=
@@ Line 10: / Line 24: @@
 OpenOffice Draw file: [[File:neo-273.odg]]
-Note that A4 of the C ROMs is missing since it bypasses the chip and comes straight from the cartridge edge. Same issue with A3 of the S ROM.
 [[Category:Chips]]

NEO-273: Difference between revisions

Revision as of 22:58, 27 January 2012

Demultiplexing

Pinout

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