Data Transmission Method And Data Format - Epson PC AX Technical Manual

PRINCIPLES OF OPERATION
2.5.3.4 Keyboard Data Input (AT mode)
REV.A
When the keyboard detects a low level signal 1n the data line it becomes ready
to receive.
Then the signal in the host clock line drops to a low level below 60 us, which
will stop keyboard transmission.
When the keyboard detects a high level in the clock line, da ta reception is
performed (counts off each group of 11 bits). After receiving the 10th bit,
the keyboard changes the signal in the data line to low level and receives one
more bit (the stop bit). The low level signal of the 11th bit teIls the host
that the data has been received.
2.5.3.5 Data Transmission Method and Data Format
TADLE 2-5-4.
DATA TRANSMISSION ME'l1IOD AND DATA FORMAT
(1) Transmission method Synchronous serial Synchronous serial
transmission transmission
(2)
Transmission rate
9600 BPS
'=.
9600 BPS
( 3)
Start bit
1
1
( 4) Stop bit
1 1
(5 )
Data length 8 bit
8
bit
( 6) Parity Odd parity None
CLOCK
2-80
OATA
I
I
00 01 0
~~
Op
STOP
START
Tl
104
us
+20%
T2 20
us
Min
T3
20
us
Min
T4
35
us
+20%
FIGURE 2-5-2. KEYBOARD DATA OU'IPUT - AT MODE