71M6545 Datasheet, PDF (22/134 Pages) Maxim Integrated Products – Four-Quadrant Metering, Phase Metrology Processors Flash/RAM Size

Data Sheet 71M6545/H
PDS_6545_009
communication with the 71M6545/H, supplying current samples and auxiliary information such as sensor
temperature via a serial data stream.
Up to three 71M6xx3 Isolated Sensors can be supported by the 71M6545/H. When a remote sensor
interface is enabled, the two analog current inputs become re-configured and a digital remote sensor
interface. For example, when control bit RMT2_E = 1, the IADC2-IADC3 analog pins are re-configured as
the digital interface pins to the remote sensor.
Each 71M6xx3 Isolated Sensor consists of the following building blocks:
• Power supply that derives power from pulses received from the 71M6545/H
• Bi-directional digital communications interface
• Shunt signal pre-amplifier
• 22-bit 2nd Order Sigma-Delta ADC Converter with precision bandgap reference (chopping amplifier)
• Temperature sensor (for digitally compensating VREF)
• Fuse system containing part-specific information
During an ordinary multiplexer cycle, the 71M6545/H internally determines which other channels are
enabled with MUX_DIV[3:0] (I/O RAM 0x2100[7:4]). At the same time, it decimates the modulator output
from the 71M6xx3 Isolated Sensors. Each result is written to CE RAM during one of its CE access time
slots.
2.2.8.2 Communication between 71M6545/H and 71M6xx3 Isolated Sensor
The ADC of the 71M6xx3 derives its timing from the power pulses generated by the 71M6545/H and as a
result, operates its ADC slaved to the frequency of the power pulses. The generation of power pulses, as
well as the communication protocol between the 71M6545/H and 71M6xx3 Isolated Sensor, is automatic and
transparent to the user. Details are not covered in this data sheet.
2.2.8.3 Control of the 71M6xx3 Isolated Sensor
The 71M6545/H can read or write certain types of information from each 71M6xx3 remote sensor.
The data to be read is selected by a combination of the RCMD[4:0] and TMUXRn[2:0]. To perform a read
transaction from one of the 71M6xx3 devices, the MPU first writes the TMUXRn[2:0] field (where n = 2, 4, 6,
located at I/O RAM 0x270A[2:0], 0x270A[6:4] and 0x2709[2:0], respectively). Next, the MPU writes
RCMD[4:0] (SFR 0xFC[4:0]) with the desired command and phase selection. When the RCMD[4:2] bits
have cleared to zero, the transaction has been completed and the requested data is available in
RMT_RD[15:0] (I/O RAM 0x2602[7:0] is the MSB and 0x2603[7:0] is the LSB). The read parity error bit,
PERR_RD (SFR 0xFC[6]) is also updated during the transaction. If the MPU writes to RCMD[4:0] before a
previously initiated read transaction is completed, the command is ignored. Therefore, the MPU must wait
for RCMD[4:2]=0 before proceeding to issue the next remote sensor read command.
The RCMD[4:0] field is divided into two sub-fields, COMMAND=RCMD[4:2] and PHASE=RCMD[1:0], as
shown in Table 4.
Table 4. RCMD[4:0] Bits
Command
RCMD[4:2]
Phase Selector
RCMD[1:0]
Associated TMUXRn
Control Field
000
Invalid
00
Invalid
---
001 Command 1
01
IADC2-IADC3
TMUXR2[2:0]
010 Command 2
10
IADC4-IADC5
TMUXR4[2:0]
011
Reserved
11
IADC6-IADC7
TMUXR6[2:0]
100
Reserved
101
Invalid
110
Reserved
111
Reserved
Notes:
1. Only two codes of RCMD[4:2] (SFR 0xFC[4:2]) are relevant for normal
operation. These are RCMD[4:2] = 001 and 010. Codes 000 and 101
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