Facit 4431 Service Instruction page 13

6.5 INPUT/OUTPUT INTERFACE
Figure 6.5 is a block diagram of the Input/
Output Interfaces. Communication between the
Facit 4431 and the host computer and local
printer is through bidirectional, asynchronous
serial V24/RS-232-C ports. A dual channel SIO
(Serial Input/output controller) performs the
parallel/serial data conversion required to
adapt and synchronize the terminals internal
parallel data to the serial format of the ex-
Z80 A
,
SID
-
4
048
--r
!--------,
.
~
~
4
Z80 A
8
UART
DATA
8
CLOCKS
BUS
.....
.
~
..
3
CONTROL
8
I
&
. -
ADDRESS
• •
Z80A
CTC
f
13
CLOCK.
___.
COUNTER
..
02
050
5
--
. .
13
ternal devices. Communications parameters such
as data rate , parity, and word lenght are se-
lected by the operator in the SET-UP MODE, and
stored from one session to the next in the
non-volatile EAROM. The Z80A CPU reads these
parameters from the EAROM upon power-up, and
uses this data to configure the SIO and the
baude rate clock generators.
TTL TO
RS232C
LINE
DRIVERS
061
....
RS232C
i.-
TO TTL
i.._
LINE
:
RECEIVERS
14-
062
__..
__:
--
.....
'-+
I/O SER. OUT
I/O DTR
I/O RTS
I/O SER. IN
I/O DSR
I/O CTS
I/O
PORT
P. SER OUT } PRINTER
P. SER IN PORT
P. ROY
-- INT
-- REQUEST
FIG 6.5 INPUT/OUTPUT, PRINTER INTERFACES
6.6 KEYBOARD SYSTEM
The keyboard is a seperate item connected to
the display unit by a flexible coiled cable.
To simplify the connection, the keyboard enco-
ding is performed on the keyboard itself pro-
ducing a serial code which is received by a
UART on the Main Logic board of the terminal.
The keyboard logic is based on the INTEL 8035
microprocessor using 2k byte program.National
character versions are jumper selectable. Key-
board encoding is done using an encoder ROM.
Depression of each encoded key or key combina-
tion produces a unique ROM address, and in
each ROM location is the code for associated
key depression(s). The selected code is then
transmitted in serial form to the keyboard
UART in the display unit. A block diagram of
the Keyboard system is shown in Fig 6.6.
SERIAL
MOD-
KEYS
STRAPS
8
SEL
2x8195
8
KEY
MATRIX
96 KEYS
IN
O U T - - - - - ;
STRAPS
2
FIG 6.6 KEYBOARD
XTAL
CPU
8035
ROM
8
8
2716 8
(2Kx8)
8