Tandy 1400LT - Page 275

TIMERKOUNTER
The program must write a control command to set the counter mode and write the count data that determines the
length
of the count operation.
Write Operations
(CS=O, RD= 1, WR=O)
Address AI A0 Write Target
40H 0 0 Counter 0
41H 0
1 Counter 1
42H 1
0 Counter 2
43H 1
1 Control word register
Control Register Format
m m m I* m m DI m
SCl SCO RWMl RWMO C
BCD
Binaly or BCD
0 Binary Count (16 Bits)
1 I BCD Count (4 Dimid
RWMl RWMO Read/Wnts Mode '
Hipher Byte Only
Lower Byte then Hipher
Select Counter or Multiple
Latch Command
sc1 sco
0 0 count., # 0
0
1 covnter t 1
NOTE.
Il,Ts=o. %=o. WR=1
12) See Reading the Counter
1
0 counter # 2
1 I 1 I MuIImIe Latch Cornrnmd 121
x. Don't care
Readmrite Mode and Count Write
No. of
Writes
Read/Write Mode
Count Register
Higher Byte Lower Byte
Low 1-byte 1 OOH nnH
High 1-byte 1 nnH OOH
Low/High 2-byte
2
nnH
(2nd write)
nnH
(1st write)
nnH
= Two-digit hexadicimal value
F-6