71m6521be Maxim Integrated Products, Inc., 71m6521be Datasheet - Page 39

• Manufacturer Part Number: 71m6521be
• Description: Energy Meter Ic
• Manufacturer: Maxim Integrated Products, Inc.

Digital I/O
The device includes up to 14 pins of general purpose digital I/O. These pins are compatible with 5V inputs (no current-limiting
resistors are needed). Some are dual function that can alternatively be used as LCD drivers (DIO4-11, 14-17) and some share
functions with the optical port (DIO1, DIO2). On reset or power-up, all DIO pins are inputs until they are configured for the
desired direction under MPU control. The pins are configured by the DIO registers and by the five bits of the LCD_NUM
register (located in I/O RAM). Once declared as DIO, each pin can be configured independently as an input or output with the
DIO_DIRn bits. A 3-bit configuration word, DIO_Rx, can be used for certain pins, when configured as DIO, to individually assign
an internal resource such as an interrupt or a timer control. Table 53 lists the direction registers and configurability associated
with each group of DIO pins. Table 54 shows the configuration for a DIO pin through its associated bit in its DIO_DIR register.
Tables showing the relationship between LCD_NUM and the available segment/DIO pins can be found in the Applications
section and in the I/O RAM Description under LCD_NUM[4:0].
V1.0
DIO
Pin number
Data Register
Direction Register
Internal Resources
Configurable
DIO
Pin number
Data Register
Direction Register
Internal Resources
Configurable
A
B
from OPT_TX UART
Table 53: Data/Direction Registers and Internal Resources for DIO Pin Groups
OPT_TXMOD=0
PB
62
16
22
Y
N
0
0
0
0
OPT_TXINV
57
17
12
N
Y
1
1
1
1
1
© 2005-2008 TERIDIAN Semiconductor Corporation
DIO_DIR0 (SFR 0xA2)
DIO_DIR2 (SFR 0xA1)
DIO2=P2 (SFR 0xA0)
DIO0=P0 (SFR 0x80)
18
Y
--
--
--
--
2
3
2
2
19
--
--
--
--
--
--
--
--
3
Figure 7: Optical Interface
OPT_TXMOD
OPT_FDC
37
20
4
4
4
Y
--
--
--
--
A
--
38
21
5
5
5
Y
--
--
--
EN
39
22
Y
--
--
6
6
6
--
--
MOD
2
DUTY
40
23
Y
--
--
--
7
7
7
--
WPULSE
A
B
DIO2
41
Y
8
0
0
B
OPT_FDC=2 (25%)
42
2
1
OPT_TXMOD=1,
Y
OPT_TXE[1:0]
9
1
1
0
DIO_DIR1 (SFR 0x91)
DIO1=P1 (SFR 0x90)
10
43
Energy Meter IC
Y
2
2
1/38kHz
Internal
11
44
Y
3
3
71M6521BE
12
--
--
--
--
DATA SHEET
OPT_TX
13
--
--
--
--
14
20
--
6
6
JANUARY 2008
V3P3
Page: 39 of 97
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