System Board Pos Register 2 (Hex 0102); 2-4. System Board; 2-5. Parallel Port Select Bits; P~S Register 2 (Hex 0102) - IBM Personal System/2 50 Technical Reference

System Board POS Register 2 (Hex 0102)
When the system board is in the setup mode, the diskette drive
controller, serial port, and parallel port are controlled by this
read/write register. Reading this register returns the current state of
these system board functions.
Bit Function
7 Disable Parallel Port Extended Mode
6. 5 Parallel Port Select
4 Enable Parallel Port
3 Serial Port Select
2 Enable Serial Port
1 Enable Diskette Drive Interface
o
Enable System Board
Figure 2-4. System Board
P~S
Register 2 (Hex 0102)
Bit 7 When set to 0, this bit allows the parallel port to be
configured as an 8-bit, parallel, bidirectional interface.
When set to 1, this bit disables the bidirectional mode.
This bit is set to 0 at power-on, and POST sets it to 1.
Bits 6, 5 These bits select the configuration of the system board
parallel port.
Bits
65
Assignment
Hex Address
Interrupt Level
00 Parallel 1 03BC - 03BF 7
01 Parallel 2 0378- 037B 7
10 Parallel 3 0278- 027B 7
1 1 Reserved
-
..... _
....
_---_
..
-
Figure 2-5. Parallel Port Select Bits
Bit 4 When this bit and bit 0 are set to 1, the system board
parallel port is enabled.
Bit 3 When set to 1, this bit sets the system board serial port as
Serial 1 (addresses hex 03F8 through 03FF), which uses
interrupt level 4. When set to 0, this bit sets the serial port
as Serial 2 (addresses hex 02F8 through 02FF), which uses
interrupt level 3.
2-8 Model 50 P~S