ade7753 Analog Devices, Inc., ade7753 Datasheet - Page 29

• Manufacturer Part Number: ade7753
• Description: Active And Apparent Energy Metering Ic With Di/dt Sensor Interface
• Manufacturer: Analog Devices, Inc.

ADE7753 Serial Read Operation
During a data read operation from the ADE7753 data is
shifted out at the DOUT logic output on the rising edge of
SCLK. As was the case with the data write operation, a data
read must be preceded with a write to the Communications
register.
With the ADE7753 in communications mode (i.e. CS logic
low) an eight bit write to the Communications register first
takes place. The MSB of this byte transfer is a 0, indicating
that the next data transfer operation is a read. The LSBs of
this byte contain the address of the register which is to be
read. The ADE7753 starts shifting out of the register data on
the next rising edge of SCLK – see Figure 54. At this point
the DOUT logic output leaves its high impedance state and
starts driving the data bus. All remaining bits of register data
are shifted out on subsequent SCLK rising edges. The serial
interface also enters communications mode again as soon as
the read has been completed. At this point the DOUT logic
REV. PrF 10/02
DOUT
SCLK
SCLK
DIN
DIN
CS
CS
t
t
1
1
SCLK
DIN
1
0
0
0
PRELIMINARY TECHNICAL DATA
t
2
X
0
Command Byte
0
t
3
Command Byte
A4 A3 A2 A1 A0
t
4
X
A4 A3 A2 A1 A0
Most Significant Byte
Figure 54– Serial Interface Read Timing Diagram
Figure 52 – Serial Interface Write Timing Diagram
X
Figure 53—12 bit Serial Write Operation
X
t
5
DB11 DB10
t
DB9
7
–29–
t
9
t
DB8
11
DB7
Most Significant Byte
output enters a high impedance state on the falling edge of the
last SCLK pulse. The read operation may be aborted by
bringing the CS logic input high before the data transfer is
complete. The DOUT output enters a high impedance state
on the rising edge of CS.
When an ADE7753 register is addressed for a read operation,
the entire contents of that register are transferred to the serial
port. This allows the ADE7753 to modify its on-chip
registers without the risk of corrupting data during a multi
byte transfer.
Note when a read operation follows a write operation, the
read command (i.e., write to communications register)
should not happen for at least 4µs after the end of the write
operation. If the read command is sent within 4µs of the write
operation, the last byte of the write operation may be lost.
The is given as timing specification t
DB7
DB7
Most Significant Byte
DB6
Least Significant Byte
DB5
DB0
DB4
t
t
11
7
DB3
DB0
DB7
Least Significant Byte
t
DB2
10
t
6
Least Significant Byte
DB1
DB7
DB0
DB0
9
.
t
t
8
12
ADE7753
t
DB0
13