Cirrus Logic CS5467 - Manual (Page 42)

CS5467
42 DS714F3
10. E
2
PROM OPERATION
The CS5467 can accept commands from a serial
E
2
PROM connected to the serial interface instead of a
host microcontroller. A high level (logic 1) on the MODE
input indicates that an E
2
PROM is connected. This
makes the CS and SCLK pins become driven outputs.
After reset and after running the initialization program,
the CS5467 begins reading commands from the con-
nected E
2
PROM.
10.1 E
2
PROM Configuration
A typical connection between the CS5467 and a
E
2
PROM is shown in Figure 13 .
The CS5467 asserts CS (logic 0), clocks SCLK, and
sends Read commands to the E
2
PROM on SDO.
Command format is identical to microcontroller mode,
except the CS5467 will not attempt to write to the EE-
PROM device. The command sequence stops when the
STOP bit in the Control register (Ctrl) is written by the
command sequence.
Figure 13 also shows the external connections that
would be made to a calibration device, such as a note-
book computer, handheld calibrator, or tester during
meter assembly, The calibrator or tester can be used to
control the CS5467 during calibration and program the
required values into the E
2
PROM.
10.2 E
2
PROM Code
The EEPROM code should do the following:
1. Set any Configuration or Control register bits, such as
HPF enables and phase compensation settings.
2. Write any calibration data to gain and offset registers.
3. Set energy output pulse width, rate, and formats.
4. Execute a Continuous Conversion command.
5. Set the STOP bit in the Control register (last).
Below is an example E
2
PROM code set.
- 7E 00 00 01
Change to page 1.
- 60 00 01 E0
Write Modes Register, turn high-pass filters on.
- 42 7F C4 A9
Write value of 0x7FC4A9 to I1
GAIN
register.
- 46 FF B2 53
Write value of 0xFFB253 to V1
GAIN
register.
- 50 7F C4 A9
Write value of 0x7FC4A9 to I2
GAIN
register.
- 54 FF B2 53
Write value of 0xFFB253 to V2
GAIN
register.
- 7E 00 00 00
Change to page 0.
- 74 00 00 04
Set LSD bit to 1 in the Mask register.
- E8
Start continuous conversions
- 78 00 01 00
Write STOP bit to the Control register (Ctrl) to
terminate E
2
PROM command sequence.
10.3 Which E
2
PROMs Can Be Used?
Several industry-standard serial E
2
PROMs can be used
with the CS5467. Some are listed below:
• Atmel AT25010, AT25020 or AT25040
• National Semiconductor NM25C040M8 or NM25020M8
• Xicor X25040SI
These serial E
2
PROMs expect a specific 8-bit com-
mand (00000011) in order to perform a memory read.
The CS5467 has been hardware programmed to trans-
mit this 8-bit command to the E
2
PROM after reset.
CS5467 EEPROM
E1
E2
MODE
SCLK
SDI
SDO
CS
SCK
SO
SI
CS
Connector to Calibrator
VD
+
5 K
5 K
Pulse Output
Counter
Figure 13. Typical Interface of E
2
PROM to CS5467