DEC VT220 Technical Manual page 204

APPENDIX C
REGISTER BIT VALUES
This appendix contains figures illustrating bit values for the
various register devices within the system box logic board
circuits. The figures are provided for reference only, and are not
meant as a guide to programming the VT220 Series terminal.
MRl A ADDRESS
MR1 B ADDRESS
B7FOH (RD)/B7FOH IWR)
B7F8H (RDI/B7FBH IWR)
o~ 06
05
04
03
02
01
00
I
!
I
Rx
I
RxiDT
ERROR
I
PAR ITY MODE
PARiTY BiTS PER
RTS I SEl MODE TYPE CHARACTER
I
I
IBAD7 Hi" .. (BADO Hi
BIT VALUES
BIT 7
0 RxRTS DISABLED
1
RxRTS ENABLED
BIT 6
0 INTERRUPT ON RxRDY
INTERRUPT ON FFULL
BIT 5
0 CHARACTER ERROR MODE
1
BLOCK ERROR MODE
BIT 3-4
00 WITH PARITY
01 FORCE PARITY
10
NO PARITY
11
SPECIAL MODE
BIT 2
0
EVEN PARITY
1 ODD PARITY
BIT 0-1 00 5 BITS PER CHARACTER
01 6 BITS PER CHARACTE R
10
7 BITS PER CHARACTER
11 8 BITS PER CHARACTER
"'.-06'&-'"
Figure C-l 2681 DUART: Mode Register 1
(MR1)
(Channel
A
and B)
C-l