71M6543F Datasheet, PDF (59/157 Pages) Maxim Integrated Products – Selectable Gain of 1 or 8 for One Current Energy Meter ICs Metrology Compensation

71M6543F/H and 71M6543G/GH Data Sheet
After reset or power up, pins SEGDIO0 through SEGDIO15 are initially DIO outputs, but are
disabled by PORT_E = 0 (I/O RAM 0x270C[5]) to avoid unwanted pulses during reset. After
configuring pins SEGDIO0 through SEGDIO15 the MPU must enable these pins by setting
PORT_E.
Once a pin is configured as DIO, it can be configured independently as an input or output. For SEGDIO0
to SEGDIO15, this is done with the SFR registers P0 (SFR 0x80), P1 (SFR 0x90), P2 (SFR 0xA0) and P3
(SFR 0xB0), as shown in Table 48.
Example: SEGDIO12 (pin 32 in Table 48) is configured as a DIO output pin with a value of 1 (high) by
writing 0 to bit 4 of LCD_MAP[15:8], and writing 1 to both P3[4]and P3[0]. The same pin is configured
as an LCD driver by writing 1 to bit 4 of LCD_MAP[15:8]. The display information is written to bits 0 to 5
of LCD_SEG12.
The PB pin is a dedicated digital input and is not part of the SEGDIO system.
The CE features pulse counting registers and each pulse counter interrupt output is internally
routed to the pulse interrupt logic. Thus, no routing of pulse signals to external pins is required in
order to generate pulse interrupts. See interrupt source No. 2 in Figure 12.
A 3-bit configuration word, I/O RAM register DIO_Rn (I/O RAM 0x2009[2:0] through 0x200E[6:4]) can be
used for pins SEGDIO2 through SEGDIO11 (when configured as DIO) and PB to individually assign an
internal resource such as an interrupt or a timer control (DIO_RPB[2:0], I/O RAM 0x2450[2:0], configures
the PB pin). This way, DIO pins can be tracked even if they are configured as outputs. Table 48 lists the
internal resources which can be assigned using DIO_R2[2:0] through DIO_R11[2:0] and DIO_RPB[2:0]. If
more than one input is connected to the same resource, the resources are combined using a logical OR.
Table 47: Selectable Resources using the DIO_Rn[2:0] Bits
Value in DIO_Rn[2:0] Resource Selected for SEGDIOn or PB Pin
0
None
1
Reserved
2
T0 (counter0 clock)
3
T1 (counter1 clock)
4
High priority I/O interrupt (INT0)
5
Low priority I/O interrupt (INT1)
Note:
Resources are selectable only on SEGDIO2 through SEGDIO11 and the
PB pin. See Table 49.
When driving LEDs, relay coils etc., the DIO pins should sink the current into GNDD (as
shown in Figure 16, right), not source it from V3P3D (as shown in Figure 16, left). This is due
to the resistance of the internal switch that connects V3P3D to either V3P3SYS or VBAT. See
6.4.6 V3P3D Switch on page 139.
Sourcing current in or out of DIO pins other than those dedicated for wake functions, for
example with pullup or pulldown resistors, must be avoided. Violating this rule leads to
increased quiescent current in sleep and LCD modes.
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