IBM PC CONVERTIBLE Technical Reference page 23

Set RS232_BASE
table entry to hex
3F8.
Move
RS232_BASE
table pointer to
next entry.
Write/read hex
AAand55to
work register at
hex2FF.
To
Part 6
No (Not attached)
- - - - - - - { Test for secondary
Figure 1-3 (Part 5 of 7). Printer/Communications Presence Test
1-16 Power-OnSelf-Test(POST)