71m6515h Maxim Integrated Products, Inc., 71m6515h Datasheet - Page 51

• Manufacturer Part Number: 71m6515h
• Description: 71m6515h Energy Meter Ic
• Manufacturer: Maxim Integrated Products, Inc.

Communication between the 71M6515H and the Host Processor
General
To ensure proper transfer of energy and other values from the 71M6515H to the host, the output data of the 71M6515H must
be read by the host each time they are ready, and no energy-related datum can be missed. This requires close synchronization
between the 71M6515H and the host.
Control Signals
Figure 19 shows the control signals between the 71M6515H and the host processor. These signals are:
TX and RX are the most essential signals for the communication between the 71M6515H and the host processor. The IRQZ
pin provides a useful output signal that can be used by the host to determine whether the 71M6515H has fresh data ready.
IRQZ can be connected to either an interrupt input or general I/O input of the host processor.
RESETZ can be used to force a hardware reset of the 71M6515H, and UARTCSZ can be used to reset (purge) the UART of
the 71M6515H communication buffers for reconfiguration. The additional pins BAUD_RATE and PULSE_INIT can be hard-
wired for configuring the communication baud rate and the pulse status, or controlled on power up by the host processor.
Note that the DIO pins of the host processor used to control the 71M6515H are not lost, since the 71M6515H can provide eight
DIO pins ((DIO0…DIO7) to act as general-purpose DIO pins.
Since the communication between the 71M6515H and its host is based on a binary protocol, it is imperative for the host to
issue a clean character stream without added bytes (UART drivers of high-level operating systems often add extra bytes to the
character stream, relying on error-detecting protocols). In case the 71M6515H loses synchronization due to unexpected bytes
sent by the host, it times out after 10ms (maximum 20ms). The 71M6515H flags a time-out condition by setting the BOOTUP
flag in the STATUS register. This happens because the incomplete or garbled data could have included a write command to the
CONFIG register or other important registers.
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TX: Serial transmit output pin of the 71M6515H
RX: Serial receive input pin of the 71M6515H
IRQZ: Interrupt output, used as “Data Ready” hardware signal of the 71M6515H (low-active)
RESETZ: Reset input pin of the 71M6515H (low-active, should be pulled up to V3P3)
UARTCSZ: UART reset input pin of the 71M6515H (low-active)
BAUD_RATE: Baud rate select input pin of the 71M6515H (optional)
PULSE_INIT: Pulse polarity select input pin of the 71M6515H (optional)
DIO
Figure 19: Connections between 71M6515H and Host
© 2005-2008 TERIDIAN Semiconductor Corporation
DIO0...DIO7
71M6515H
BAUD_RATE
PULSE_INIT
UARTCSZ
RESETZ
IRQZ
T X
RX
3.3V
DIO_2
DIO_3
DIO_4
DIO_5
Energy Meter IC
RX
IRQ or DIO_1
T X
Host
DATA SHEET
71M6515H
MARCH 2008
V1.4