Z89175 Datasheet, PDF (26/68 Pages) Zilog, Inc. – Voice Processing Controllers

Z89175/Z89176
Voice Processing Controllers
Zilog
PIN FUNCTIONS (Continued)
Port 3 (P37-P31). Port 3 is a 7-bit, CMOS compatible port
with three fixed inputs (P33-P31) and four fixed outputs
(P37-P34). It is configured under software control for in-
put/output, counter/timers, interrupt, and port handshakes.
Pins P31, P32, and P33 are standard CMOS inputs; out-
puts are push-pull.
Two on-board comparators can process analog signals on
P31 and P32 with reference to the voltage on P33. The an-
alog function is enabled by programming bit 1 of the Port 3
Mode Register. Port 3, pin 3 is a falling edge interrupt in-
put. P31 and P32 are programmable as rising, falling or
both edge-triggered interrupts (IRQ register bits 6 and 7).
P33 is the comparator reference voltage input. Access to
counter/timer1 is made through P31 (T_IN) and P36 (T_OUT).
Handshake lines for ports 0, 1, and 2 are available on P31
through P36.
Port 3 also provides the following control functions: hand-
shake for Ports 0, 1, and 2 (/DAV and RDY); three external
interrupt request signals (IRQ3-IRQ1); timer input and out-
put signals (T_IN and T_OUT) (Figure 14).
Comparator Inputs. Port 3, pins P31 and P32 all have a
comparator front end. The comparator reference voltage,
pin P33, is common to both comparators. In analog mode,
P31 and P32 are the positive inputs to the comparators
and P33 is the reference voltage supplied to both compar-
ators. In digital mode, pin P33 can be used as a P33 reg-
ister input or IRQ1 source.
Table 5. Port 3 Pin Assignments
Pin
I/O
P31
IN
P32
IN
P33
IN
P34
OUT
P35
OUT
P36
OUT
P37
OUT
Notes:
HS = Handshake Signals
D = DAV
R = RDY
CTC1
TIN
TOUT
AN IN
AN1
AN2
REF
Int.
IRQ2
IRQ0
IRQ1
P0 HS
D/R
R/D
P1 HS
D/R
R/D
P2 HS
D/R
R/D
EXT
DM
26
PRELIMINARY
DS97TAD0100