L8708H datasheet(22/66 Pages) ZILOG

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Z86L88/81/86/87/89/73

IR/Low-Voltage Microcontroller

P R E L I M I N A R Y

DS96LV00800

PIN FUNCTIONS (Continued)

Port 3 (P37-P31). Port 3 is a 7-bit, CMOS compatible three

fixed input and four fixed output port. Port 3 consists of

three fixed input (P33-P31) and four fixed output (P37-

P34), and can be configured under software control for In-

put/Output, Interrupt, Port handshake, Data Memory func-

tions and output from the counter/timers. P31, P32, and

P33 are standard CMOS inputs; outputs are push-pull.

Two on-board comparators process analog signals on P31

and P32 with reference to the voltage on Pref1 and P33.

The analog function is enabled by programming the Port 3

Mode Register (bit 1). P31 and P32 are programmable as

rising, falling, or both edge triggered interrupts (IRQ regis-

ter bits 6 and 7). Pref1 and P33 are the comparator refer-

ence voltage inputs. Access to the Counter Timer edge de-

tection circuit is through P31 or P20 (see CTR1

description). Other edge detect and IRQ modes are de-

scribed in Tables (3-6). Handshake lines Ports 0, 1, and 2

are available on P31 through P36.

Port 3 provides the following control functions: handshake

for Ports 0, 1, and 2 (/DAV and RDY); three external inter-

rupt request signals (IRQ2-IRQ0); Data Memory Select

(/DM) (Table 3).

Port 3 also provides output for each of the counter/timers

and the AND/OR Logic. Control is performed by program-

ming bits D5-D4 of CTR1, bit 0 of CTR0 and bit 0 of CTR2.

Comparator Inputs. In Analog Mode, Port 3 (P31 and

P32) have a comparator front end. The comparator refer-

ence is supplied to P33 and Pref1. In this mode, the P33

internal data latch and its corresponding IRQ1 is diverted

to the SMR sources (excluding P31,P32, and P33) as

shown in figure 41. In digital mode, P33 is used as D3 of

the Port 3 input register which then generates IRQ1 as

shown in Figure 17.

When P31 is used for counter timer input (demodulation

mode), input is always taken from the P31 digital input

buffer whether or not analog mode is enabled).

Notes: Comparators are powered down by entering STOP

mode. For P31-P33 to be used in a Stop-Mode Recovery

source, these inputs must be placed into digital mode.

Comparator Outputs. These may be programmed to be

outputted on P34 and P37 through the PCON register (Fig-

ures 16,38).

/RESET (Input, active Low). Initializes the MCU. Reset is

accomplished either through Power-On, Watch-Dog Tim-

er, Stop-Mode Recovery, Low Voltage detection, or exter-

nal reset. During Power-On Reset and Watch-Dog Timer

Reset, the internally generated reset drives the reset pin

Low for the POR time. Any devices driving the external re-

set line should be open-drain in order to avoid damage

from a possible conflict during reset conditions. Pull-up is

provided internally.

Table 3. Pin Assignments

I/O

C/T

Comp.

Int.

P0 HS

P1 HS

P2 HS

Ext

Pref1

RF1

P31

AN1

IRQ2

D/R

P32

AN2

IRQ0

D/R

P33

RF2

IRQ1

D/R

P34

OUT

AO1

R/D

P35

OUT

T16

R/D

P36

OUT

T8/16

R/D

P37

OUT

AO2

P20

I/O

Notes:

D = /DAV

R = RDY

HS = Handshake Signals

L8708H Datasheet(PDF) 22 Page - Zilog, Inc.

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