Keyboard
I expect the HW of the TMC-600 keyboard encoder to be very similar to the Telmac 1800 however not 100% sure. OUT 3 is used to set the key latch, the key latch will address one of the keys as in the table below. After the key latch is set EF3 indicates if that specific key is pressed or not. This mechanism means that the CPU needs to scan all keys. This does take some more processor load compared to the solution used in the COMX-35 which uses the CDP 1871 for similar functionality.
Key latch |
bit 5 |
0 |
0 |
0 |
0 |
1 |
1 |
1 |
1 |
||
|
bit 4 |
0 |
0 |
1 |
1 |
0 |
0 |
1 |
1 |
||
bit 2 |
bit 1 |
bit 0 |
bit 3 |
0 |
1 |
0 |
1 |
0 |
1 |
0 |
1 |
0 |
0 |
0 |
0 |
( |
\ |
H |
P |
X |
SPACE |
CAPS |
|
0 |
0 |
1 |
! |
) |
A |
I |
Q |
Y |
DEL |
|
|
0 |
1 |
0 |
" |
* |
B |
J |
R |
Z |
ESC |
LINE |
|
0 |
1 |
1 |
# |
+ |
C |
K |
S |
≈ |
RIGHT |
↑ |
|
1 |
0 |
0 |
$ |
< |
D |
L |
T |
ƒ |
LEFT |
→ |
|
1 |
0 |
1 |
% |
= |
E |
M |
U |
÷ |
RIGHT |
RETURN |
|
1 |
1 |
0 |
& |
> |
F |
N |
V |
~ |
LEFT |
↓ |
|
1 |
1 |
1 |
/ |
? |
G |
O |
W |
BREAK |
SHIFT |
← |
|