71M6521BE Datasheet, PDF (40/97 Pages) Teridian Semiconductor Corporation – Energy Meter IC

71M6521BE
Energy Meter IC
DATA SHEET
JANUARY 2008
DIO Pin n Function
DIO_DIR [n]
0
1
Input
Output
Table 54: DIO_DIR Control Bit
Additionally, if DIO6 is declared an output, it can be configured as dedicated pulse output (WPULSE = DIO6) using the
DIO_PW register. In this case, DIO6 is under CE control. DIO4 and DIO5 can be configured to implement the EEPROM
Interface.
The PB pin is a dedicated digital input. If the optical UART is not used, OPT_TX and OPT_RX can be configured as dedicated
DIO pins (DIO1, DIO2, see Optical Interface section).
A 3-bit configuration word, I/O RAM register, DIO_Rx (0x2009[2:0] through 0x200E[6:4]) can be used for certain pins, when
configured as DIO, to individually assign an internal resource such as an interrupt or a timer control (see Table 55 for DIO pins
available for this option). This way, DIO pins can be tracked even if they are configured as outputs.
Tracking DIO pins configured as outputs is useful for pulse counting without external hardware.
When driving LEDs, relay coils etc., the DIO pins should sink the current into GNDD (as shown in Figure 8,
right), not source it from V3P3D (as shown in Figure 8, left). This is due to the resistance of the internal
switch that connects V3P3D to either V3P3SYS or VBAT.
When configured as inputs, the dual-function (DIO/SEG) pins should not be pulled above V3P3SYS in
MISSION and above VBAT in LCD and BROWNOUT modes. Doing so will distort the LCD waveforms of the
other pins. This limitation applies to any pin that can be configured as a LCD driver.
71M6521B
V3P3SYS
VBAT
V3P3D
DIO1
3.3V
R
LED
71M6521B
V3P3SYS
VBAT
V3P3D
DIO1
R
3.3V
LED
DGND
DGND
Not recommended
Recommended
Figure 8: Connecting an External Load to DIO Pins
The PB pin is a dedicated digital input. In addition, if the optical UART is not used, OPT_TX and OPT_RX can be configured
as dedicated DIO pins DIO1 and DIO2. Thus, in addition to the 12 general-purpose DIO pins (DIO4…DIO11, DIO14…DIO17),
there are three additional pins that can be used for digital input and output.
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