![](http://datasheet.mmic.net.cn/230000/7540_datasheet_15567442/7540_26.png)
HARDWARE
1-8
7540 Group User
’
s Manual
PIN DESCRIPTION
Table 1 Pin description
Pin
Vcc, Vss
Function
Apply voltage of 2.2 to 5.5 V to Vcc, and 0 V to Vss.
Reference voltage input pin for A-D converter
Chip operating mode control pin, which is always connected to Vss.
Reset input pin for active
“
L
”
Input and output pins for main clock generating circuit
Connect a ceramic resonator or quartz crystal oscillator between the X
IN
and X
OUT
pins.
For using RC oscillator, short between the X
IN
and X
OUT
pins, and connect the capacitor and resistor.
If an external clock is used, connect the clock source to the X
IN
pin and leave the X
OUT
pin open.
When the ring oscillator is selected as the main clock, connect X
IN
pin to V
SS
and leave X
OUT
open.
8-bit I/O port.
I/O direction register allows each pin to be individually pro-
grammed as either input or output.
CMOS compatible input level
CMOS 3-state output structure
Whether a built-in pull-up resistor is to be used or not can be de-
termined by program.
5-bit I/O port
I/O direction register allows each pin to be individually pro-
grammed as either input or output.
CMOS compatible input level
CMOS 3-state output structure
CMOS/TTL level can be switched for P1
0
, P1
2
and P1
3
8-bit I/O port having almost the same function as P0
CMOS compatible input level
CMOS 3-state output structure
8-bit I/O port
I/O direction register allows each pin to be individually programmed as either input or output.
CMOS compatible input level (CMOS/TTL level can be switched for P3
6
and P3
7
).
CMOS 3-state output structure
P3
0
to P3
6
can output a large current for driving LED.
Whether a built-in pull-up resistor is to be used or not can be de-
termined by program.
Function expect a port function
Name
Power source
(Note 1)
Analog reference
voltage
CNVss
Reset input
Clock input
I/O port P0
I/O port P1
V
REF
CNVss
RESET
X
IN
P0
0
/CNTR
1
P0
1
/TY
OUT
P0
2
/TZ
OUT
P0
3
/TX
OUT
P0
4
–
P0
7
Notes 1: V
CC
= 2.4 to 5.5 V for the extended operating temperature version and the extended operating temperature 125
°
C version.
2: P2
6
/AN
6
and P2
7
/AN
7
do not exist for the 32-pin version, so that Port P2 is a 6-bit I/O port.
3: P3
5
and P3
6
/INT
1
do not exist for the 32-pin version, so that Port P3 is a 6-bit I/O port.
Key-input (key-on wake up
interrupt input) pins
Timer Y, timer Z, timer X and
timer A function pin
P1
0
/RxD
1
P1
1
/TxD
1
P1
2
/S
CLK1
/S
CLK2
P1
3
/S
RDY1
/S
DATA2
P1
4
/CNTR
0
P2
0
/AN
0
–
P2
7
/AN
7
P3
0
–
P3
5
P3
6
/INT
1
P3
7
/INT
0
I/O port P2
(Note 2)
I/O port P3
(Note 3)
Serial I/O1 function pin
Serial I/O1 function pin
Serial I/O2 function pin
Timer X function pin
Input pins for A-D converter
Interrupt input pins
X
OUT
Clock output
PIN DESCRIPTION