Commodore 128 Programmer's Reference Manual page 404

394 COMMODORE 128
10 INPUT "SELECT DEVICE NUMBER";D%
20 INPUT "SELECT SECONDARY ADDRESS";S%
30 INPUT "NAME OF FILE OR CONTROL REGISTER";A$
40 OPEN 9,D%,S%,A$
50 GOSUB 80
60 CLOSE 9
70 END
80 REM PLACE SUBROUTINE HERE
90 RETURN
0
THE INPUT/OUTPUT
PINOUTS
THE SERIAL PORT
The Serial Port is a daisy chain arrangement designed to let the Commodore 128 computer
communicate with more than one device, such as Commodore disk drives and printers.
Up to five devices can be connected at one time. The serial bus can transmit control
signals from the computer, send data onto the bus, and receive data from the bus. Data
or control signals are routed to the proper device by opening a specific bus address
ranging from 4 to 31. Typically, addresses 4 and 5 are reserved for printers, and
addresses 8 through 11 are for the disk drive.
Six lines are used in serial bus operation—three input and three output. The three
input lines bring data, control and timing signals into the computer. The three output
lines send data, control and timing signals from the computer to the external devices.
See Hardware Specifications (Chapter 16) for details on the C128 serial bus protocol.
SERIAL I/O
PIN TYPE
1
2
3
4
5
6
SERIAL SRQIN
GND
SERIAL ATN IN/OUT
SERIAL CLK IN/OUT
SERIAL DATA IN/OUT
RESET
Figure 12-5. Serial Port Pinouts
u
USER PORT (RS-232 CHANNEL)
The User Port (RS-232 Channel) connects the Commodore 128 to the outside
world, such as another Commodore computer. It is directly connected to the 6526 CIA
#1 chip. Figure 12-6 shows the User Port pinouts. Table 12-4 defines the pinouts.