Z86319 Datasheet, PDF (12/23 Pages) Zilog, Inc. – PS/2 MOUSE CONTROLLER

Z86319
PS/2 Mouse Controller
PIN FUNCTIONS (Continued)
Port 3 (P33, P31). Port 3 is a 2-bit, CMOS-compatible
port with two fixed input lines (P33, P31). These two lines
can also be used as the interrupt sources IRQ2 and IRQ1.
P31 can also be configured as a timer input. Both lines can
be configured through ROM mask selection to sink or
source current emulating a 100K pull-up or pull-down re-
Zilog
sistor (Figure 12). Port 33-31 can be accessed through
the P3 register. The upper 4 bits of this 8-bit register al-
ways reads “1111.” Bit D2 reads 0 and Bit D0 reads 1. Bits
D3 and D1 represent P33 and P31 respectively (see Fig-
ure 36).
Pad
P31
Pull-Up Enable
(Mask Option)
Pull-Down/Enable
(Mask Option)
Data Latch
IRQ2, TIN
Pull-Up Enable
(Mask Option)
Pad
P33
Pull-Down/Enable
(Mask Option)
Data Latch
IRQ1
Figure 12. Port 3 P33, P31 Configuration
12
PRELIMINARY
DS97KEY1605