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Technical Reference Guide
Compaq Deskpro 4000N and 4000S Personal Computers
First Edition - September1997
4-43
The 87307 I/O Controller provides 11 general purpose pins that can be individually configured as
either inputs or outputs. These pins are mapped as two general purpose ports and software-
accessable through the registers shown below.
GPIO Port 1 Data, I/O Addr. 078h, (87307 I/O Controller)
Bit Function
7..4 GPIO17..GPIO14: Not used.
3 GPIO13 (config. as input). Bus Fraction (BF2)
2 GPIO12 (config. as input): CPU Bus Speed
Read 0, 60 MHz
Read 1, 66 MHz
1,0 GPIO11,10 (config. as inputs): Bus Fraction (ratio) BF1,0
Read 00, 2/5 bus/core speed ratio
Read 10, 1/3 bus/core speed ratio
Read 01, ½ bus/core speed ratio
Read 11, 2/7 bus/core speed ratio
GPIO Port 1 Direction, I/O Addr. 079h, (87307 I/O Controller)
GPIO Port 1 Output Type, I/O Addr. 07Ah, (87307 I/O Controller)
GPIO Port 1 Pullup Control, I/O Addr. 07Bh, (87307 I/O Controller)
GPIO Port 2 Data, I/O Addr. 07Ch, (87307 I/O Controller)
Bit Function
7..4 GPIO27..24 (config. as I/O): X bus bits <5..2>
3 GPIO23 (config. as input): Ring Wake Up (Serial Modem)
Read 0, Ring indicate active
Read 1, Ring indicate inactive
2 GPIO22 (config. as output): NIC I/F Enable.
Write 0 to enable.
Write 1 to disable.
1,0 GPIO21 Not used.
GPIO Port 2 Direction, I/O Addr. 07Dh, (87307 I/O Controller)
GPIO Port 2 Output Type, I/O Addr. 07Eh, (87307 I/O Controller)
GPIO Port 2 Pullup Control, I/O Addr. 07Fh, (87307 I/O Controller)