Changes
Arnold4
,The final cost down models came just before the release of the Amstrad plus.
The same chip was used within the late CPC464 and CPC6128.It performs the operations of the PAL used in the CPC6128, the Gate-Array used in older CPCs and the CRTC. =CRTC=
In CRTC terms it operates almost the same as the CRTC within the Plus ASIC.
=Costdown IC pinout information=
The following information relating to the pins of the IC was tested and verified by Gerald:
In 464 mode :
* the /ROM2 signal is always high : ROM7 selection is not handled on board.
* the /CAS1 signal is always high : RAM extension is not handled on board.
In 6128 mode :
* the /ROM2 signal is handled on board.* the /CAS1 like AMSDOS ROM is handled on board6128/DDI1. When /EXT tied low, with the expected result of getting garbage instead of base RAM /ROM2 will be active when using RAM selection other than C0ROM7 is selected. When /EXT is floating (ie pulled up), /ROM2 will be active when ROM0 is selected.* CPC does 464 will get stuck after displaying the copyright message and before the "BASIC 1.0" messageas nothing is connected to /ROM2.* the /CAS1 is handled on board. On 464, expect garbage instead of base RAM when using RAM selection other than C0 and no RAM extension connected.
==Extension RAM management==
In 464 mode :
In 6128 mode :
==ROM7 and ROMDIS in 6128 mode==
* Well, no luck. ROMDIS does not prevent internal ROM7 to be selected, as on regular 6128, unlike plus range.* ROMDIS act as an output when ROM7 is selected (However I need to re-check that it is TBC : only happening on ROM 7ROM7/0 ?)* ROMDIS act as the DDI DDI1 ROMDIS as it is active even during ram access 10943-0accesses.<br />The following picture shows the ROM detection routine : Selection of ROM7, followed by a read at 0xC000 where ROMDIS is active as well as /ROM2[[File:CPC464PREASIC 6128mode ROM7.png]]
==/EXP==
==Bonus==