VT82C686B
Parallel Port Registers
These registers are located at I/O ports which are offsets from
“LPTBase” (index E6h of the Super-I/O configuration
registers). LPTBase is typically set to allow these ports to be
accessed at the standard parallel port address range of 378-
37Fh.
Port LPTBase+0 – Parallel Port Data .............................RW
Port LPTBase+3 – Parallel Port EPP Address............... RW
Port LPTBase+4 – Parallel Port EPP Data Port 0......... RW
Port LPTBase+5 – Parallel Port EPP Data Port 1......... RW
Port LPTBase+6 – Parallel Port EPP Data Port 2......... RW
Port LPTBase+7 – Parallel Port EPP Data Port 3......... RW
7-0 Parallel Port Data
Port LPTBase+1 – Parallel Port Status............................RO
7
6
5
4
3
BUSY#
0
Printer busy, offline, or error
1
Printer not busy
ACK#
0
Data transfer to printer complete
1
Data transfer to printer in progress
PE
0
Paper available
Port LPTBase+400h – Parallel Port ECP Data / Cfg A RW
Port LPTBase+401h – Parallel Port ECP Config B....... RW
Port LPTBase+402h – Parallel Port ECP Extd Ctrl...... RW
1
No paper available
SLCT
0
1
Printer offline
Printer online
7-5 Parallel Port Mode Select
000 Standard Mode....................................... default
001 PS/2 Mode
ERROR#
0
1
Printer error
Printer OK
................................... always read 1 bits
010 FIFO Mode
2-0 Reserved
011 ECP Mode
100 EPP Mode
101 -reserved-
110 -reserved-
111 Configuration Mode
Parallel Port Interrupt Disable
Port LPTBase+2 – Parallel Port Control ........................RW
................................. always read back 1
7-5 Undefined
4
3
2
1
0
Hardware Interrupt
4
0
Disable ...................................................default
0
1
Enable an interrupt pulse to be generated on
the high to low edge of the fault. An interrupt
will also be generated if the fault condition is
asserted and this bit is written from 1 to 0.
Disable the interrupt generated on the asserting
edge of the fault condition
1
Enable
Printer Select
0
Deselect printer ......................................default
1
Select printer
Printer Initialize
0
Initialize Printer......................................default
3
2
Parallel Port DMA Enable
1
Allow printer to operate normally
0
Disable DMA unconditionally
Automatic Line Feed
1
Enable DMA
0
Host handles line feeds...........................default
Parallel Port Interrupt Pending
1
Printer does automatic line feeds
0
Interrupt not pending
Strobe
1
Interrupt pending (DMA & interrupts disabled)
0
No data transfer......................................default
This bit is set to 1 by hardware and must be written to
0 to re-enable interrupts
1
Transfer data to printer
1
0
FIFO Full ......................................................... RO
0
FIFO has at least 1 free byte
1
FIFO full or cannot accept byte
FIFO Empty......................................................... RO
0
FIFO contains at least 1 byte of data
1
FIFO is completely empty
Revision 1.71 June 9, 2000
-49-
Register Descriptions - Super-I/O I/O Ports
ETC [ ETC ]
