Datasheet
MAX71020
Single-Chip Electricity Meter AFE
27Maxim Integrated
Table 8. Hardware Control Register Map (continued)
*Default values given for standard CE code (2520 sample frequency, gain = 9).
CE Interface Description
The CE reads the ADC and stores its results in the 1KB
block at 0x000. Since all CE operations are 32 bits wide,
the CE data memory occupies the first 256 32-bit loca-
tions, from 0x000 to 0x0FF.
Note: The CE interface described in the data sheet is a
description of the released CE code. Contact your rep-
resentative or Maxim Integrated technical support for the
latest information on alternate CE codes.
CE Data Format
All CE words are 4 bytes. Unless specified otherwise, they
are in 32-bit two’s complement format (-1 = 0xFFFFFFFF).
Calibration para meters are copied to CE data memory by
the host controller before enabling the CE. Internal vari-
ables are used in internal CE calculations. Input variables
allow the MPU to control the behavior of the CE code.
NAME
BYTE
ADDRESS
R/W
DEFAULT
VALUE*
DESCRIPTION
VSTAT 0x312 R —
AFE Supply Voltage Status. Bits 1:0 reflect system power status:
00: System power-OK: V
V3P3A
> 3.0V
01: System power-low: 2.8V < V
V3P3A
< 3.0V
11: System power-fail: V
V3P3A
< 2.8V
RESET 0x322 WO — Write 0x8100 0000 to this register to reset the AFE.
TEMP_CNF 0x323 R/W
0x0000
0000
Configures aspects of the temperature measurement subsystem. Loaded by
the LE.
BIT NAME DESCRIPTION
1:0 Reserved —
3:2 TEMP_PER
Sets the period between temperature measurements.
01: Measure every accumulation cycle
10: Continuous measurement
Other values disable automatic updates.
4 TEMP_SYS
When set, V
V3P3SYS
is measured at every temperature
measurement cycle
31:5 Reserved —
TEMP_START 0x324 R/W
0x0000
0000
Write 0x8000 0000 to start a temperature conversion cycle. When conversion is
complete, the AFE clears bit 31 and returns the register to zero.
SPI_SAFE 0x325 R/W
0x0000
0000
Write 0x8000 0000 to this word to lock the SPI port. When the SPI port is
locked, no read or write operations are possible except to the SPI_SAFE
register. Clearing this register to zero disables the SPI lock and restores normal
operation.
METER_EN 0x326 R/W
0x0000
0000
Enables aspects of the AFE.
BIT NAME DESCRIPTION
0 ADC_E
Enable ADC and VREF buffer. Must be set by host
following initialization.
1 CE_E Enable CE. Must be set by host following initialization.
31:2 Reserved —