Z86319 Datasheet, PDF (10/23 Pages) Zilog, Inc. – PS/2 MOUSE CONTROLLER

Z86319
PS/2 Mouse Controller
Zilog
PIN FUNCTIONS (Continued)
Port 2 (P27-P20). Port 2 is an 8-bit, bit programmable, bi-
directional, CMOS-compatible I/O port. These eight I/O
lines can be configured under software control to be input
or output, independently. Bits programmed as outputs
may be globally programmed as either push-pull or open-
drain. When configured as inputs, P20 and P22 have 10
kOhm (typical) pull-up resistors (Figure 9). However, P21
and P23 do not have resistors (Figure 10).
When configured as inputs, P24-P27 are configured with a
voltage divider. The voltage divider consists of an internal
25K pull-up resistor (Figure 11), and a 7.5K pull-down re-
sistor. The input levels on P24-P27 are adjusted for con-
nection to the emitters of the opto-transistors and switch at
a voltage level of 0.4 V_DD (± 300 mV). For input voltages
on P24-P27, refer to Table 3.
Table 3. P24-P27 Input Open Circuit Voltage
(No off-chip resistance)
V_DD
4.5V
5.0V
5.5V
Min
0.95V
1.05V
1.15V
Max
1.15V
1.25V
1.39V
Open-Drain
OE
V_DD
10 Kohm, ±20%
Pad
Out
In
Figure 9. Port 2 P20, P22 Configuration
10
PRELIMINARY
DS97KEY1605