The Telmac 2000 uses the CDP 1864 for video output. For details on the CDP 1861 please see the data sheets for this chip or the 'summary' on the CDP 1861 page. The Telmac 2000 controls the CDP 1864 via INP 4 to switch the display off, INP 1 to switch the display on and EF1 to indicate the display status. OUT 1 is used to step the background colour, from blue to black to green to red and then back to blue.
The Telmac 2000 firmware is as far as I know the same as the Telmac 1800 firmware and as such the CDP 1864 is not fully supported. The resolution of 64 x 48 is used with interrupt routine entry point at @8146 and display memory at @7F00-@807F. Note that this address range always includes the last RAM page (even in a 4 or 16 KB RAM system due to the RAM mirroring) and also the first 80 bytes of ROM. This results in a display with the lower part of the screen unusable due to the fact that this part of the screen memory is in ROM
The colour RAM can be written by first setting the colour latch (OUT 4 with value 1) and then writing to address location @8000-@83FF. The Telmac 2000 has 1024 x 4 bit colour RAM for the 64 x 48 resolution only 384 x 4 bit are used where every 8 horizontal pixels have the same colour.
The display status is an active low output signal occurring for a period of four horizontal cycles prior to the beginning and end of the 196 line display window. The signal is used by the firmware interrupt routine to indicate the last 'row' of the display area.