Changes
CRTC
,/* Datasheets */
CRTCs 1 and 2 have a fixed VSYNC width value of 16. VSYNC width can be configured with Register 3 on CRTCs 0, 3 and 4.
The bit 0 of port B of the PPI changes to 1 as soon as the VSYNC signal is produced by the CRTC.
== The 6845 Registers ==
* On types 0 and 1, if a Write Only register is read from, "0" is returned.
* CRTC types 3 and 4 are identical in every way, except for the unlocking mechanism , split-screen and 8-bit printer port functionalities specific to the ASIC.
* See the document "Extra CPC Plus Hardware Information" for more details.
== Datasheets ==
* [[Media:hd6845.hitachi.pdf|HD6845S (Hitachi) (]] aka type Type 0)]]* [[Media:UM6845-UMC.pdf|UM6845 (UMC) (aka type 0)]]aka Type 0* [[Media:Um6845r.umc.pdf|UM6845R (UMC) (]] aka type Type 1)]]* [[Media:Mc6845.motorola.pdf|MC6845 (Motorola) (aka type 2)]] aka Type 2 [[Media:Mc6845.pdf|Other datasheet version]]* [[Media:CPC_Plus_Asic_Schematic.GIF|AMS40489 (Amstrad)]] aka Type 3* [[AMS40226 (Amstrad)]] aka Type 4*[[Media:CRTC-5-HD6345.pdf|HD6345 (Hitachi) (]] aka type Type 5)]] - Upgraded pin-compatible CRTC chip with advanced functionalities [https://thecheshirec.at/2024/05/07/un-crtc6345-sur-amstrad-cpc/ Upgrading the CPC to HD6345]
== Unused clones ==
* [[CM607P ]] a Bulgarian clone made in Pravetz factory]* [[EF6845P ]] by Thomson Semiconductors]* [[UM6845E ]] by UMC]* [[SY6845EA ]] by Synertek* [[F68B45P]] by Freescale
* CRTC6545 (MOS, Rockwell, Synertek) is pin-compatible with the 6845 and only has minor differences
* [https://github.com/hoglet67/BeebFpga/blob/dev/src/common/mc6845.vhd BeebFpga] [https://github.com/MiSTer-devel/Amstrad_MiSTer/blob/master/rtl/UM6845R.v MiSTer] [https://opencores.org/websvn/filedetails?repname=System09&path=%2FSystem09%2Ftrunk%2Frtl%2FVHDL%2Fcrtc6845.vhd OpenCores] Verilog/VHDL implementations of the 6845
*[[Synchronising with the CRTC and display]] : technic and details on the relationship between Gate Array and CRTC.
[[Category:Hardware]] [[Category:CPC Internal Components]] [[Category:Electronic Component]] [[Category:Programming]] [[Category:Datasheet]] [[Category:Graphic]]
