Tandy 1400LT - IV-12. Keyboard Interface

IV-12. Keyboard
The TANDY 1400LT can use an Internal keyboard and an External keyboard.
Figure 4-17 shows the block diagram in GATE4. The data from Internal keyboard
is a parallel 8-bit data, and from
External keyboard is a serial 10 bit data. The data is selected in GATE4 (selector A) and goes to the data bus
through
1/0 port 060H (subset of 82C55). Internal keyboard is controlled by IC50. IC50 is a single chip, 8-bit
microprocesser containing an 8-bit CPU, ROM, RAM,
I/O ports and control circuitry. IC50 generates strobe signal
at every key-stroke.(KP2 1)
Figure 4-18 shows IC50 and peripheral circuitry.
'8 BIT
SHIFT
- REGISTER
DATA BW
EXTERNAL KEYBOARD I
GATE4
DATA
OATA 1
SELECTOR PARALLEL DATA
A
-
I/O
PORT
60H-62H
Figure 4-17. Keyboard-1 (The Block Diagram in the GATE4)
DO KDO 00
,I
m
II
D7 KD7
GATE4
i TO
KTO
IC50
22!+P20
P24
P25
P28
P27
P21
P22
P23
BFWT I *
Figure 4-1 8. Keyboard-2 (IC50 and Peripheral Circuitry)
4-16