Tandy 102 Service Manual page 31

Time Read Sequence
The CPU sets the
pPD1 990AC
to the time read mode with the "110" pattern of the C0-C2 and strobe
signal.
Then the CPU sets the register shift mode with the "100" pattern of the C0-C2, and reads the data of
time and date information from the DATA OUT terminal. At the same time, the CPU sends the PA3
signal passing through the PIO for the read timing clock.
Y6 -
WR*--
M26
32.768 kHz
M2
RESET
RESET
-Y y
M O
M U MCL
F-
C19
0.047)J
25V
VB
14 OE D
DATA
TP CS STB 12
C18
20P
I
T
JJPD I990AC M
18
x1 O
CO Cl C2 DATAIN CLK
13 C17 20P
Y6 -
WR*--
C19
0.047)j
25V
7
CO C1
C2 DATAIN CLK
13
C1720P
32.768 kHz
O - N M
a a a. a
Figure 4-13. Time Read Sequence of ,uPD1990AC
VB
14 OE DATA TP CS STB 12
C18
20P
OUT
11
JJPD1990AC M18 x1p