Hello all,
I’m studying the HP-71B internals, especially the display driver. To do that, I try to modify/improve existing LEX and got stuck with one particular entry. While studying the DSPLEX that changes the behaviour of the display (such as “small fonts, invert etc) I was surprised how easy the implementation of the small font feature was. Changing fonts from normal to small is achieved just by setting ROWDRV to the value “0000800360041008”.
What does the ROWDRV entry point for the HP-71B. The IDS volume 1 says : “Row lines (16 nibbles). Should be set by software as follows: 8001400220041008”. This is set accordingly in “LCDINI” (see IDS volume 3 page SB&DVR-34) and says “Bit pattern for driving display”.
Notice that the hex sequence is symmetrical from the middle (: 80014002 Vs 20041008).
Is there anybody that can give a definition of the pattern and how it affects the display behaviour ?
Thanks
Alain Robillard