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Functional Description
CPB902
C P B 9 0 2 U s e r M a n u a l
55
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Figure 4.22:
COM3-COM6 Ports: Simplified Interface Circuit Diagram
RTX RS-232
RXD_COM (TTL)
RO
DI
DE
H/F
A
B
Y
Z
RTX RS-422/485
MUX 2 to 1
TXD_COM (TTL)
Other RS-232 Signals (TTL)
EN_COM
TXEN_485
HF_485
120
120
1
2
3
4
(Port 0x31C, bit N+1)*
(Port 0x31C, bit N-3)*
(Port 0x31D, bit N-3)*
*) N - COM-port number (3, 4, 5, 6)
Terminators
TXD
RXD
+5V
1
2
3
4
5
6
7
8
9
10
IDC10 Connectors
J5/J7/J9/J11
DCD (TX+/D+)
DSR (TX-/D-)
RXD
RTS
TXD
CTS
DTR (RX+)
RI (RX-)
GND
VCC
In RS-232 mode the terminators should not be enabled. In RS-485 or RS-422 modes the jumpers
should be set on appropriate pinpads: J6 (COM3), J8 (COM4), J10 (COM5) and J12 (COM6). In
RS-485 mode jumper 1-2 should be set on terminating modules; in RS-422 "point-to-point" mode
jumper 3-4 should be set. Switching to RS-422/RS-485 modes is done in BIOS Setup. For COM1 –
COM6 ports base addresses, please, refer to Tables 4.2 and 4.3.
4.3.12 FDD/LPT
Port
The LPT1 port of CPB902 supports EPP and ECP operation modes. ECP is the default mode.
LPT is routed to J15 connector shared with FDD port. Switching between LPT and FDD ports is
performed in BIOS Setup.
LPT1 uses IRQ7 interrupt line, IRQ6 is assigned to FDD port. Interrupts from these ports can be
disabled and switched for use by ISA bus devices in BIOS Setup program (see sections
and
).
A printer is connected to J15 header via ACS00011 FCD25F cable with DB25F connector.
A floppy disk drive is connected to J15 header via the ACS00002 FC26-60 26-thread ribbon cable
and CDM01 (469535.030) transition module, which is installed directly on 34-pin FDD connector.
The table below describes pin assignments of the J15 connector.