Datasheet

ADE7953 Data Sheet
Rev. B | Page 56 of 72
UART Read
A read from the ADE7953 via the UART interface is initiated
by the master sending a packet of three frames. If the first frame
has the value 0x35, a read is being issued. The second and third
frames contain the address of the register being accessed. When
the ADE7953 receives a legal packet, it decodes the command
(see Figure 73).
The frame time is 2.08 ms. A frame-to-frame delay (t
1
) of 4 ms
max provides a 50% buffer on the frame time without needlessly
slowing the communication. When the read packet is decoded,
the ADE7953 sends the data from the selected register out on the
Tx pin (see F4 and F5 in Figure 73). This occurs approximately
0.1 ms after the complete frame is received. This data can be 1,
2, 3, or 4 bytes long, depending on the size of the register that is
being accessed. The register data is sent LSB first. After the last
frame of register data is sent from the ADE7953, a packet-to-
packet delay (t
2
) of 6 ms min is required before any incoming
data on the Rx pin is accepted. This packet-to-packet timeout
ensures that no overlap is possible.
UART Write
A write to the ADE7953 via the UART interface is initiated by
the master sending a packet of three frames. If the first frame
has the value 0xCA, a write is being issued. The second and
third frames contain the address of the register being accessed.
The next two frames contain the data to be written. When the
ADE7953 receives a legal packet, it decodes the command as
follows:
 If the number of frames obtained after the initial packet is
the same as the size of the register specified by F2 and F3, the
packet is legal and the corresponding register is written.
 If the number of frames does not equal the size of the
specified register, the command is illegal and no further
action is taken.
After the last frame of data is received on the Rx pin, a wait
period of t
2
is required before any incoming data on the Rx pin
is treated as a new packet. This operation is shown in Figure 74.
F1
READ/
WRITE
Rx
Tx
F2
ADDRESS
MSB
F3
ADDRESS
LSB
t
1
F1
READ/
WRITE
F2
ADDRESS
MSB
t
1
t
1
F4
DATA
LSB
F5
DATA
MSB
t
1
t
2
t
1
09320-142
Figure 73. UART Read
F1
READ/
WRITE
Rx
Tx
F2
ADDRESS
MSB
F3
ADDRESS
LSB
t
1
F1
READ/
WRITE
F2
ADDRESS
MSB
t
1
t
1
F4
DATA
LSB
F5
DATA
MSB
t
1
t
2
t
1
09320-143
Figure 74. UART Write