Rainbow Electronics 71M6542G User Manual

Page 16

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16

© 2008–2011 Teridian Semiconductor Corporation

v1.1

I/O RAM

Mnemonic

I/O RAM

Location

71M6541D/E

(hex)

71M6542F

(hex)

FIR_LEN[1:0]

210C[2:1]

1

1

ADC_DIV

2200[5]

1

1

PLL_FAST

2200[4]

1

1

MUX_DIV[3:0]

2100[7:4]

3

3

MUX0_SEL[3:0]

2105[3:0]

0

0

MUX1_SEL[3:0]

2105[7:4]

A

A

MUX2_SEL[3:0]

1

2104[3:0]

1

9

MUX3_SEL[3:0]

1

2104[7:4]

1

1

RMT_E

2709[3]

1

1

DIFFA_E

210C[4]

1

1

DIFFB_E

210C[5]

0

0

EQU[2:0]

2106[7:5]

0 or 1

0, 1 or 2

CE Code

--

CE41B016201

2

CE41B016601

3

Equations

--

0, 1

0, 1 and 2

Current Sensor Type

--

1 Local Shunt

and

1 Remote Shunt

1 Local Shunt

and

1 Remote Shunt

Applicable Figure

--

Figure 3

Figure 5

Notes:

1.

Although not used, set to 1 (the sample data is ignored by the CE)

2.

71M654x with 71M6201 remote sensor (200 Amps)

3.

71M654x with 71M6601 remote sensor (60 Amps)

TERIDIAN updates the CE code periodically. Please contact your local TERIDIAN representative
to obtain the latest CE code and the associated settings. The configuration presented in this table
is set by the MPU demonstration code during initialization.

Using settings for the I/O RAM Mnemonics listed in

Table 1

and

Table 2

that do not match

those required by the corresponding CE code being used results in undesirable side effects
and must not be selected by the MPU. Consult your local TERIDIAN representative to obtain
the correct CE code and AFE / MUX settings corresponding to the application.

For a basic single-phase application, the IAP-IAN current input is configured for differential mode,
whereas the VA pin is single-ended and is typically connected to the phase voltage via a resistor divider.
The IBP-IBN differential input may be optionally used to sense the Neutral current. This configuration
implies that the multiplexer applies a total of three inputs to the ADC. For this configuration, the
multiplexer sequence is as shown in

Figure 6

. In this configuration IAP-IAN, IBP-IBN and VA are

sampled, the extra conversion time slot (i.e., slot 2) is the optional Neutral current, and the physical
current sensor for the Neutral current measurement may be omitted if not required.

For a standard single-phase application with tamper sensor in the neutral path, two current inputs can be
configured for differential mode, using the pin pairs IAP-IAN and IBP-IBN. This means that the multiplexer
applies a total of three inputs to the ADC. In this application, the system design may use two locally
connected current sensors via IAP-IAN and IBP-IBN, as shown in

Figure 2

, and configured as differential

inputs. Alternately, the IAP-IAN pin pair is configured as a differential input and connected to a local current
shunt, and IBP-IBN is configured to connect to an isolated 71M6x01 isolated sensor (i.e., RMT_E = 1), as
shown in

Figure 3

. The VA pin is typically connected to the phase voltage via resistor dividers. For this

configuration, the multiplexer frame is also as shown in

Figure 6

and time slot 2 is unused and ignored by

the CE, as the samples corresponding to the remote sensor (IBP-IBN) do not pass through the
multiplexer and are stored directly in CE RAM. The remote current sensor channel is sampled during the
second half of the multiplexer frame and its timing relationship to the VA voltage is precisely known so
that delay compensation can be properly applied.

The 71M6542F adds the ability to sample a second phase voltage (applied at the VB pin), which makes it
suitable for meters with two voltage and two current sensors, such as meters implementing Equation 2 for
dual-phase operation (P = VA*IA+VB*IB).

Figure 7

shows the multiplexer sequence when four inputs are

processed with locally connected sensors, as shown in

Figure 3

. When using one local and one remote

sensor (

Figure 5

), the multiplexer sequence is also as shown in

Figure 7

.

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