71M6543F Maxim, 71M6543F Datasheet - Page 27

• Manufacturer Part Number: 71M6543F
• Description: The 71M6543F/71M6543H are Teridian's 4th-generation polyphase metering system-on-chips (SoCs) with a 5MHz, 8051-compatible MPU core, low-power real-time clock (RTC) with digital temperature compensation, flash memory, and LCD driver
• Manufacturer: Maxim

CK_FIR clock cycles is:
A common use of the zero-crossing pulses is to generate interrupts in order to drive real-time clock
software in places where the mains frequency is sufficiently accurate to do so and also to adjust for
crystal aging. A common use for the SAG pulse is to generate an interrupt that alerts the MPU when mains
power is about to fail, so that the MPU code can store accumulated energy and other data to EEPROM
before the V3P3SYS supply voltage actually drops.
2.3.6.1 XPULSE and YPULSE
Pulses generated by the CE may be exported to the XPULSE and YPULSE pulse output pins. Pins
SEGDIO6 and SEGDIO7 are used for these pulses, respectively. Generally, the XPULSE and YPULSE
outputs can be updated once on each pass of the CE code.
See
2.3.6.2 VPULSE and WPULSE
Referring to
bits in an 8-bit FIFO and outputs them at a specified interval. This permits the CE code to calculate the
VPULSE and WPULSE outputs at the beginning of its code pass and to rely on hardware to spread them
over the multiplexer frame. As seen in
frame. As also seen in
the delay to the first pulse update and the interval between subsequent updates. The LSB of the
PLS_INTERVAL[7:0] register is equivalent to 4 CK_FIR cycles (CK_FIR is typically 4.9152MHz if PLL_FAST=1
and ADC_DIV=0, but other CK_FIR frequencies are possible; see the ADC_DIV definition in
PLS_INTERVAL[7:0]=0, the FIFO is deactivated and the pulse outputs are updated immediately.
The MUX frame duration in units of CK_FIR clock cycles is given by:
If PLL_FAST=1:
MUX frame duration in CK_FIR cycles = [1 + (
If PLL_FAST=0:
MUX frame duration in CK_FIR cycles = [3 + 3*(
PLS_INTERVAL[7:0]
Since the FIFO resets at the beginning of each multiplexer frame, the user must specify
PLS_INTERVAL[7:0] so that all of the possible pulse updates occurring in one CE execution are output
before the multiplexer frame completes. For instance, the 71M6543 CE code outputs six updates per
multiplexer interval, and if the multiplexer interval is 1950 CK_FIR clock cycles long, the ideal value for
the interval is 1950/6/4 = 81.25. However, if PLS_INTERVAL[7:0] = 82, the sixth output occurs too late and
would be lost. In this case, the proper value for PLS_INTERVAL[7:0] is 81 (i.e., round down the result).
Since one LSB of
If the FIFO is enabled (i.e., PLS_INTERVAL[7:0] ≠ 0), hardware also provides a maximum pulse width feature
in control register PLS_MAXWIDTH[7:0] (I/O RAM 0x210A) . By default, WPULSE and VPULSE are negative
pulses (i.e., low level pulses, designed to sink current through an LED). PLS_MAXWIDTH[7:0] determines the
maximum negative pulse width T
according to the formula:
If PLS_MAXWIDTH = 255 or PLS_INTERVAL=0, no pulse width checking is performed, and the pulses
default to 50% duty cycle.
The polarity of the pulses may be inverted with the control bit PLS_INV (I/O RAM 0x210C[0]). When
PLS_INV is set, the pulses are active high. The default value for PLS_INV is zero, which selects active low
pulses.
v1.2
5.4 CE Interface Description
PLS_INTERVAL[7:0] = floor ( Mux frame duration in CK_FIR cycles / CE pulse updates per Mux frame / 4 )
Figure
PLS_INTERVAL[7:0]
9, during each CE code pass the hardware stores exported WPULSE and VPULSE sign
in units of CK_FIR clock cycles is calculated by:
Figure
© 2008–2011 Teridian Semiconductor Corporation
9, the I/O RAM register PLS_INTERVAL[7:0] (I/O RAM 0x210B[7:0]) controls
MAX
on page
T
is equal to 4 CK_FIR clock cycles, the pulse time interval T
in units of CK_FIR clock cycles based on the pulse interval T
MAX
Figure
T
= (2 * PLS_MAXWIDTH[7:0] + 1) * T
I
FIR_LEN
= 4*
120
FIR_LEN
9, the FIFO is reset at the beginning of each multiplexer
PLS_INTERVAL[7:0]
for details.
+1) * (
+1) * (
ADC_DIV
ADC_DIV
71M6543F/H and 71M6543G/GH Data Sheet
+1) * (
+1) * (
MUX_DIV
MUX_DIV
I
)] * [150 / (
)] * [48 / (
Table
I
ADC_DIV
in units of
ADC_DIV
71.) If
+1)]
I
+1)]
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