71M6533 Datasheet, PDF(66/132 Page) Teridian Semiconductor Corporation

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71M6533 Datasheet, PDF (66/132 Pages) Teridian Semiconductor Corporation – Energy Meter IC

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71M6533/G/H and 71M6534/H Data Sheet

System

Power

(V3P3SYS)

PB or wake-

up timer

WAKE

15 CK32

cycles

MPU Mode

LCD

BROWNOUT

FDS_6533_6534_004

PLL_OK

time

Figure 28: Wake Up Timing

2.5.2 Wake on Timer

If the part is in SLEEP or LCD mode, it can be awakened by the wake-up timer. Until this timer times out,

the MPU is in reset due to WAKE being low. When the wake-up timer times out, the WAKE signal rises

and within three CK32 cycles, the MPU begins to execute. The MPU can determine whether the timer

woke it by checking the AUTOWAKE interrupt flag (IE_WAKE).

The wake-up timer begins timing when the part enters LCD or SLEEP mode. Its duration is controlled by

WAKE_PRD[2:0] and WAKE_RES. WAKE_RES selects a timer LSB of either 1 minute (WAKE_RES = 1) or

2.5 seconds (WAKE_RES = 0). WAKE_PRD[2:0] selects a duration of from 1 to 7 LSBs.

The timer is armed by WAKE_ARM = 1. It must be armed at least three RTC cycles before SLEEP or

LCD_ONLY is initiated. Setting WAKE_ARM presets the timer with the values in WAKE_RES and WAKE_PRD

and readies the timer to start when the processor writes to the SLEEP or LCD_ONLY bits. The timer is

reset and disarmed whenever the processor is awake. Thus, if it is desired to wake the MPU periodically

(every 5 seconds, for example) the timer must be rearmed every time the MPU is awakened.

2.6 Data Flow

The data flow between the Compute Engine (CE) and the MPU is shown in Figure 29. In a typical application,

the 32-bit CE sequentially processes the samples from the voltage inputs on pins IA, VA, IB, and VB,

performing calculations to measure active power (Wh), reactive power (VARh), A2h, and V2h for four-quadrant

metering. These measurements are then accessed by the MPU, processed further and output using the

peripheral devices available to the MPU. Figure 29 illustrates the CE/MPU data flow.

Pulses

Samples

Pre-

Processor

IRQ

Data

MPU

Post -

Processor

Processed

Metering

Data

I/O RAM (Configuration RAM)

Figure 29: MPU/CE Data Flow

Rev 2

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