MC6847T1

Comparison of the MC6847 and MC6847T1 using PRINT CHR$ and direct screen pokes in a loop while in upper and lower code mode.1)

VDG / MODE PRINT CHR$ SCREEN RAM POKE
MC6847
MC6847T1 Uppercase
MC6847T1 Lowercase

Simple print chr$ loop:

10 CLS(0)
20 FOR I=0 TO 255
30 PRINT CHR$(I);
40 NEXT
50 GOTO 50

SCREEN POKE LOOP

Simple loop to poke values 0-255 directly into screen RAM:

10 CLS(0)
20 FOR I=0 TO 255
30 POKE 1024+I, I
40 NEXT
50 GOTO 50

MC6847T1 LOWER CASE MODE

Put the MC6847T1 into lower case mode:

1 'http://www.retrogamingtimes.com/magazine/?issue=103&page=203&theme=christmas
10 POKE &H0167,&H39:'put RTS into RVEC3 to skip JMP to CONSOLE OUT
20 POKE &HFF22,&H50:'PIA2 VDG Control - switch in lower with green border

COMPATIBLE SOFTWARE

  • Color File II
  • Color Scripsit II
  • Scott Adams adventure games
  • OS-9 Level 1 version 2 I believe did (using XMODE)…
  • NitrOS-9 level 1 for sure does.
  • Both Mikeyterm and Greg-E-Term did as well.

RTS

1)
Also note that the MC6847 and MC6847T1 character bitmap drawing has subtle differences. In particular, note the hash mark and asterisk differences between MC6847 and T1 version.
This website uses cookies. By using the website, you agree with storing cookies on your computer. Also you acknowledge that you have read and understand our Privacy Policy. If you do not agree leave the website.More information about cookies