AN408
A Design Guide to SPI F-RAM™ Processor Companion - FM33256B
Author: Harsha Medu
Associated Part Family: FM33256B
Associated Code Examples: CE204087
Related Application Notes: click here
AN408 provides an overview and design guidelines for the SPI F-RAM real-time clock (RTC) Processor Companion part
- FM33256B. This document also includes a typical application and an example code. For information on the basic SPI
operation, refer to the application note AN304 - SPI Guide for F-RAM.
Contents
1
2
3
4
5
6
7
1
Introduction ..................................................................1
Two Logical Devices in One ........................................1
Typical Application.......................................................2
Processor Companion Features ..................................2
4.1 System Power-On Reset with
pin ...............3
4.2 Early Power-Fail Warning ...................................3
4.3 Event Counter .....................................................4
4.4 Serial Number .....................................................4
Real-Time Clock ..........................................................4
5.1 Backup Power .....................................................6
5.2 RTC Calibration ..................................................6
Power Cycle Considerations........................................6
Summary .....................................................................7
8 Related Application Notes ........................................... 7
9 PSoC 3 User Module ................................................... 7
10 Pseudo Code Examples .............................................. 7
10.1 Enable RTC Oscillator ........................................ 8
10.2 Set RTC Time/Date............................................. 8
10.3 Set VTP Voltage Detect Trip Point ...................... 9
10.4 Read RTC Registers ........................................... 9
10.5 Read Event Counters........................................ 10
10.6 SPI Processor Companion Write ...................... 11
10.7 SPI Processor Companion Read ...................... 12
Document History............................................................ 13
Worldwide Sales and Design Support ............................. 14
Introduction
The FM33256B is a 256-Kbit serial (SPI) F-RAM memory product, which offers an integrated processor companion
and an RTC. The processor companion section includes a power-on system reset, low-voltage detect, a watchdog
timer, an early power-fail warning, an event counter, automatic switchover to backup power, and a lockable 64-bit
serial number. It employs an industry-standard SPI, which is used to access the memory, the processor companion,
and the RTC. The FM33256B operates over a 2.7 V-to-3.6 V power supply range with the maximum SPI frequency of
16 MHz. It is available in an SOIC-14 package.
2
Two Logical Devices in One
Even though FM33256B is a single device, it is internally organized as two logical devices as shown in Figure 1.
Figure 1. Two Logical Devices with Unique Opcodes
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A Design Guide to SPI F- AM™ Processor Companion - FM33256B
The memory is one logical device, and the companion/RTC is the other logical device. This helps to integrate both
the functionalities without affecting each other. Each has its own address space and is accessed via the SPI. The
F-RAM is accessed through the standard memory opcodes (0x02 for Write and 0x03 for Read). The processor
companion/RTC is accessed through special opcodes (0x12 for Write and 0x13 for Read).
Note: For the complete list of opcodes, refer to Table 2.
3
Typical Application
A typical application of FM33256B is shown in Figure 2. It is shown as an example with external components, their
typical values, and connections to other system devices. This application is a line-operated (AC powered) system
with a microcontroller (the FM33256B device), and other passive components. The example microcontroller has a
dedicated SPI port. All microcontrollers may not have this port; in such cases, the SPI protocol may be implemented
in firmware and bit-banged through GPIO pins.
Note: Bit banging is a technique used for serial communications. It uses firmware instead of a dedicated hardware.
Firmware directly sets and samples the state of pins on the microcontroller, and is responsible for all parameters of
the signal like timing, levels, synchronization and so on.
Figure 2. FM33256B Reference Schematic
4
Processor Companion Features
The FM33256B device integrates all the necessary processor supervisor features that a designer may need.
The companion features include:
System Power-On Reset (POR) with
o Low -Voltage Detect
o Watchdog
o Manual reset
Early power-fail warning
pin
Event counters
Lockable serial number
The following sections describe each of these in detail.
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A Design Guide to SPI F- AM™ Processor Companion - FM33256B
4.1
System Power-On Reset with
pin
The FM33256B product provides a processor-reset signal when the system powers up and whenever a system fault
or manual override (manual hardware reset) occurs. The
pin is primarily used to drive a reset to the processor,
but can be used as an input to provide a hardware reset to the system. The
pin does not reset or clear any
FM33256B internal registers.
There are two trigger sources that can drive reset LOW: a Low Voltage (LV) Detect circuit and the Watchdog Timer
as shown in Figure 3.
Figure 3. Reset Trigger Sources
VDD
LV Detect
~ 150K
Lockout
RST
+
VDD
VTP
Watchdog
Timer
WDE
At power-up, the
pin is driven LOW as VDD rises toward its nominal operating value. The point at which the
pin is released is determined by VTP (Voltage Trip Point), an internal trip voltage that is always compared to V DD. The
internal pull-up resistor (approximately 150 kΩ) on the
pin eliminates the need for an external resistor. When
tripped, the reset circuit times out after approximately 65 ms (30 ms minimum, 100 ms maximum). You may set VTP
(2 bits, VTP1, VTP0 in register 18h) to one of four values: 2.6 V, 2.75 V, 2.9 V, or 3.0 V.
The other source of trigger for the
pin is the watchdog timer, a free-running, user-programmable timer that can
be set to time out as soon as 60 ms or as long as 1.8 seconds. The timer settings are stored in nonvolatile registers
(registers 0Bh and 0Ch), so there is no need to reinitialize these values or the trip voltage setting again. The
watchdog timer is controlled by the enable bit WDE (register 0Ch, bit 7). The Watchdog Timer works as a window
timer which allows for a delayed start.
There are two ways for the watchdog timer to trigger a reset. First, the Early Watchdog Timer Fault (EWDF in register
09h, bit 7) forces a reset condition when a restart occurs too early (before the programmed start time (register 0Bh)
for the Watchdog Timer window is reached). Second, the Late Watchdog Timer Fault (LWDF) forces a reset condition
when the timer restart occurs too late (the programmed end time (register 0Ch) for the Watchdog Timer window is
exceeded). The timer may be restarted at any time within the timeout window by writing 1010b to the Watchdog
Restart register (register 0Ah).
When a reset condition occurs, the device will set one of the three flags to indicate the source of the reset in the
register 09h: EWDF, LWDF, and POR. These bits are battery-backed during power-down. After power is restored, the
system host can read these bits to determine the cause of the reset. The host must clear these bits after reading
them.
A manual hardware reset may be provided in the system by simply connecting a momentary contact switch to the
pin. The
pin detects an external LOW input condition and responds by driving the
signal LOW for
100 ms (maximum). This effectively filters and debounces a reset switch. Note that in all reset cases, the chip
internally drives a Lockout signal that serves to block any SPI traffic and abort any pending write accesses to the
F-RAM.
4.2
Early Power-Fail Warning
The F-RAM integrated Processor Companion features a general-purpose comparator that can be used to generate
an early power-fail interrupt (PFI). This warning signal can drive a microcontroller interrupt input and must occur
before VDD drops too low to save all critical data to the nonvolatile RAM. The processor companion’s early power-fail
interrupt can also be used as a warning to the system to stop conducting critical activity during a brownout condition.
For more information, refer to the application note AN400 - Generating a Power-Fail Interrupt using the F-RAM
Processor Companion.
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A Design Guide to SPI F- AM™ Processor Companion - FM33256B
4.3
Event Counter
The FM33256B device integrates a 16-bit event counter for tamper detection or other event-logging purposes. The
counter has an input pin (CNT) that is edge-triggered and polarity that is user-defined. The event, or edge, must be
CMOS-logic level. The counter control register is nonvolatile and counter values are either battery-backed or
nonvolatile based on the Nonvolatile/Volatile Counter (NVC, in register 0Dh, bit 7) user selection.
The event counter can be operated in two modes.
Continuous mode (POLL = 0, register 0Dh, bit 1)
Polled mode (POLL = 1, register 0Dh, bit 1)
In continuous mode, the CNT pin is continuously monitored for any event and the event counter is incremented when
an event is detected. The polarity of the event can be either a rising edge (Counter Polarity bit, CP = 1, register 0Dh,
bit 0) or a falling edge (CP = 0, register 0Dh, bit 0). The events which occur as fast as 1 KHz can be detected in this
mode. Depending on the application, you can set the event counter to work on either V DD or VBAK. If events occur
when power is down, event counter should work on V BAK (NVC = 0 in register 0Dh, bit 7). Otherwise, it can be
configured to work on VDD (NVC = 1 in register 0Dh, bit 7) which will result in longer battery life.
Note: In continuous mode, a pull-up resistor on CNT pin should be connected appropriately to either the backup
supply VBAK or VDD.
Continuous mode is not suitable for detecting tamper events which are generally one-time or low-frequency events
and can occur when power is down. In such cases, polled mode can be used. Polled mode works only with
battery-backed (NVC = 0, register 0Dh, bit 7) and rising- edge detection (CP = 1, register 0Dh, bit 0) configuration. In
polled mode, the CNT pin is polled once every 125 ms resulting in a reduced power consumption and longer battery
life. The value in the event counter may not represent the actual number of tamper events, but a positive value
indicates a tamper.
Note: In polled mode, the CNT pin has an internal pull-up resistor and therefore no external pull-up is required.
A typical application in Figure 2 shows a normally-closed switch connected between the CNT pin and ground (or a
system case or chassis). The CNT pin is set to polled mode, which occasionally samples the pin in order to minimize
the battery drain. There are no external resistors required for this case. The event counter is configured to detect a
rising edge (CP = 1, register 0Dh, bit 0) on the CNT pin. When the switch is open, a tamper event is registered and
the counter increments.
4.4
Serial Number
The F-RAM processor companion provides a 64-bit lockable serial number (register 10h to register 17h in Table 1).
The serial number provides a unique way of identifying each product. The serial number has unlimited writes until the
lock-bit is set by the user.
5
Real-Time Clock
A real-time clock (RTC) counts time in steps of seconds and can report time, day of the week, calendar day, week,
and year. It can be used to record time when certain system events occur. The RTC consists of an oscillator and
counters that derive the time/calendar information, and several registers that hold the time and RTC control settings.
The RTC will run continuously even if the main power fails as long as a 3-V backup power source is connected to the
VBAK input pin. A backup source can be either a 3-V battery or a super capacitor.
The default factory settings disable the RTC oscillator. To start and configure the RTC, the
C
bit (register 00h,
bit 7) must first be set to ‘0’. Then, the clock and calendar registers must be written to reflect the current time, day,
and date. The RTC register map is shown in Table 1.
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A Design Guide to SPI F- AM™ Processor Companion - FM33256B
Table 1. RTC Register Map
The 32.768-kHz oscillator is divided down through a series of counters. The first counter divides it by 32,768 to derive
the 1-Hz signal for the seconds counter. The next counter uses the seconds counter to drive a signal once per minute
to the minutes counter. Subsequent counters continue to divide down until there is one pulse per hour, month, and
year driving their respective counters. The counters hold the time and date information that is memory-mapped
(locations 02h through 08h) into the RTC address space. Because the FM33256B uses different opcodes for the
companion register space, they do not appear as F-RAM locations. You may read and write the time and date by
reading and writing these locations without affecting the F-RAM locations.
In the FM33256B, the RTC data may be read without interrupting the RTC operation. When the RTC is read by
writing the ‘R’ bit in the control register (register 00h, bit 0) with a ’1’, a snapshot is taken of the current time-day-date
and stored in the registers where it can be read by the host. The snapshot ensures that the time doesn’t change
between successive reads from the host. However, internally, the RTC will be running normally. Similarly, during RTC
writes, the registers hold the data written by the host and wait to transfer it to the RTC counters after all the time-daydate information has been written and the ‘W’ bit (register 00h, bit 1) is cleared. If W = 0, writes to the RTC registers
are ignored. For more information on RTC read and write, refer to Setup Example
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A Design Guide to SPI F- AM™ Processor Companion - FM33256B
5.1
Backup Power
The RTC, event counter, and various control settings are maintained by using a backup power source on the VBAK pin
even if the primary power source is removed. The VBAK source may be a battery or a large-value super capacitor. For
more information, refer to AN404 - F-RAM RTC Backup Supply (VBAK pin) and UL Compliance.
When using a super capacitor as the backup source, the capacitor can discharge over a long period to a point where
the VBAK voltage drops out of spec and the RTC stops functioning, resulting in the loss of backup data. To avoid this
situation, the charge on the capacitor needs to be restored. For different types of charging, refer to AN401 - Charging
Methods for the F-RAM RTC Backup Capacitor.
5.2
RTC Calibration
RTC calibration is required primarily to compensate the frequency shift due to crystal tolerance, temperature effect,
and load-capacitance mismatch. A 512-Hz signal brought out on the ACS (Alarm/Calibration/SquareWave) pin is
used for calibration. For more information about calibration, refer to AN402 - F-RAM RTC Oscillator Design Guide.
5.2.1
Setup Example
The following example is a setup procedure that describes the correct sequence for power-up, initialization, and
register settings:
1.
Apply VDD power.
2.
Apply battery to the VBAK pin. If a super capacitor is used, the trickle charger may be set (VBC = 1). Optionally set
the FC bit. If a battery is used, make VBC = 0.
3.
Set the VDD voltage trip point bit, VTP if you prefer a setting higher than the default setting (lowest of the four
settings; 2.6 V).
4.
Enable the RTC oscillator (set
5.
Enter the RTC calibration mode (CAL = 1).
6.
Determine the RTC clock error and sign by monitoring the 512-Hz output (ACS pin). Use a frequency counter.
7.
Write the error correction sign to Calibration Sign bit (CALS, register 01h, bit 5) and value to CAL (4:0). Refer to
the Calibration Adjustments table provided in the datasheet.
8.
Exit the RTC calibration mode (CAL = 0).
9.
Set the Write bit (W bit) to enable writing the time-day-date values to the RTC.
C
= 0).
10. Write the time-day-date values to registers 02h – 08h.
11. Clear the W bit to start the RTC with the new values.
12. Resume normal operation.
To read the RTC, follow this simple three-step procedure:
6
1.
Set the Read (R bit in register 00h, bit 0) which takes a snapshot of the RTC registers (assumes R bit is
previously at logic 0).
2.
Issue the Read Processor Companion command (RDPC = 0x13), starting at the address 02h, and read seven
RTC bytes (02h – 08h).
3.
Clear the R bit to prepare for the next RTC read.
Power Cycle Considerations
To protect the F-RAM from corrupting the data during power cycles, it is recommended that the MCU’s
(SPI Slave
Select) control pin be held inactive as VDD powers up and powers down. In many cases, this may be as simple as a
pull-up resistor 1 on the MCU’s output pin that drives the FM33256B C (Chip Select) pin. As the system
microcontroller powers up, its outputs will tristate before the power supply reaches sufficient voltage to turn various
internal circuits on, thereby allowing the pull-up resistor to keep the signal at VDD. Similarly, at power-down, the VDD
voltage reaches a point where it allows the outputs to “let go”, again allowing the pull-up resistor to do its job. For
more information, refer to the application note AN302 - F-RAM SPI Read & Write and Data Protection During Power
Cycles.
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A Design Guide to SPI F- AM™ Processor Companion - FM33256B
Apart from C , you should also consider the VDD power-up ramp rate, power-down ramp rate, and power-up to first
access specifications. The power-up ramp rate should be slower than 50 µs/V and the power-down ramp rate should
be slower than 100 µs/V. FM33256B keeps the
pin LOW for tRPU time at power-up (VDD > VTP). Therefore, you
should wait for 100 ms (max) before the device can be accessed at power-up.
7
Summary
This application note summarizes the features of the FM33256B device. This document also provides a typical
application, design guidelines, and example pseudo codes for the FM33256B device.
8
Related Application Notes
AN407 - A Design Guide to I2C F-RAM Processor Companions – FM31278, FM31276, FM31L278, and
FM31L276
9
AN400 - Generating a Power-Fail Interrupt using the F-RAM Processor Companion
AN401 - Charging Methods for the F-RAM RTC Backup Capacitor
AN402 - F-RAM RTC Oscillator Design Guide
AN404 - F-RAM RTC Backup Supply (VBAK pin) and UL Compliance
PSoC 3 User Module
The PSoC 3-based user module project to access F-RAM processor companion is provided with this application note.
See the user guide provided with the project for more information.
10
Pseudo Code Examples
A summary of the op-codes of FM33256B is given in Table 2.
Table 2. Summary Table of Op-Codes
Name
Op-Code
Address
Data
Action
WREN
0000_0110b
-
-
WRITE
0000_0010b
2 bytes
Memory data in
READ
0000_0011b
2 bytes
Memory data out
Reads data from F-RAM array
WRDI
0000_0100b
-
-
Clears WEL
RDSR
0000_0101b
-
Status Register data out
Read WPEN, BP(1:0), WEL bits
WRSR
0000_0001b
-
Status Register data in
Write WPEN and BP(1:0) bits
RDPC
0001_0011b
1 byte
Register data out
Companion/RTC register read
WRPC
0001_0010b
1 byte
Register data in
Companion/RTC register write
#define nvRAM_WREN
Sets WEL
Writes data to F-RAM array if WEL = 1.
When C goes HIGH, WEL is cleared.
0x06
#define nvRAM_RTC_WRITE_CMD 0x12
#define nvRAM_RTC_READ_CMD 0x13
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A Design Guide to SPI F- AM™ Processor Companion - FM33256B
10.1
Enable RTC Oscillator
/************************** Enable RTC Oscillator
*******************************/
data[0] = 0x00;
// Data for clearing the
bit
WRITE_RTC (0x00,
// Sets the address to Register 00h
data, // Writes data 0x00 which clears the
0x01); // Number of bytes to be written
10.2
bit
Set RTC Time/Date
/************************** Set RTC time/date *******************************/
// Step #1 Set W bit which allows writes to RTC registers
data[0] = 0x02;
// Data for setting the W bit
WRITE_RTC (0x00,
// Sets the address pointer to Register 00h
data, // Writes data 0x02 which sets the W bit
0x01); // Number of bytes to be written
// Step
data[0]
data[1]
data[2]
data[3]
data[4]
data[5]
data[6]
#2 Write time/date to RTC Registers
= 0x00;
// Seconds set to 00
= 0x10;
// Minutes set to 10
= 0x14;
// Hours set to 14 (2 PM)
= 0x03;
// Day set to the third day of the week
= 0x04;
// Date set to the fourth day in March
= 0x03;
// Month set to March
= 0x08;
// Year set to 2008
WRITE_RTC (0x02,
data,
0x07);
// Sets the address pointer to Register 02h
// Writes time/date
// Number of bytes to be written
// RTC does not start to run yet.
// Step #3 Clear W bit to start RTC with the exact time
data[0] = 0x00;
// data=0x00 clears the W bit
WRITE_RTC (0x00,
data,
defined
// Sets the address pointer to Register 00h
// Data=0x00 clears the W bit to start RTC with time
// in Step #2. The 8th clock of data byte defines the
actual
0x01);
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// start of the RTC.
// Number of bytes to be written
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A Design Guide to SPI F- AM™ Processor Companion - FM33256B
10.3
Set VTP Voltage Detect Trip Point
/********************* Set VTP Voltage Detect Trip Point
**************************/
// From the factory, VTP bits are cleared to 0. If user wants to set trip point
to
// the higher setting, then write VTP bits to 11b in Reg 18h control register.
data[0] = 0x03;
// Data for setting both the VTP bits
WRITE_RTC (0x18,
// Sets the address pointer to Register 0Bh
data, // Writes data 0x03 which sets the VTP bits
0x01); // Number of bytes to be written
10.4
Read RTC Registers
/************************** Read RTC Registers *******************************/
// Step #1 Set R bit which takes snapshot of RTC registers
data[0] = 0x01;
// Data for setting the R bit
WRITE_RTC (0x00,
// Sets the address pointer to Register 00h
data, // Writes data 0x01 which sets the R bit
0x01); // Number of bytes to be written
// Step #2 Read RTC Registers
READ_RTC (0x02,
// Sets the address pointer to Register 02h
data,
// Data buffer to read RTC registers
0x07);
// Number of bytes to be read
//
//
//
//
//
//
//
//
data
0x59
0x15
0x14
0x03
0x04
0x03
0x08
buffer contains the following
– Seconds
– Minute
– Hour
– Third day of the week
- Fourth day in March
- March
- 2008
// Step #3 Clear R bit
data[0] = 0x00;
WRITE_RTC (0x00,
data,
0x01);
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// data=0x00 clears the W bit
// Sets the address pointer to Register 00h
// Data=0x00 clears the R bit to allow RTC read next time
// Number of bytes to be written
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10.5
Read Event Counters
/************************** Read Event Counters
*******************************/
// Step #1 Set RC bit which takes snapshot of both counter registers
data[0] = 0x09;
// Data for setting the RC bit and keeps CP=1
WRITE_RTC (0x0D,
// Sets the address pointer to Register 0Dh
data, // Writes data 0x09 which sets the R bit
0x01); // Number of bytes to be written
// Step #2 Read Event Counter
READ_RTC (0x0E,
// Sets the address pointer to Register 0Dh
data,
// Data buffer to read RTC registers
0x02);
// Number of bytes to be read
// data buffer contains the following
// 0x1A – CounterByte0 reads out LSB 0x1A (decimal 26)
// 0x00 – CounterByte1 reads out MSB 0x00
// Step #3 Clear RC bit
data[0] = 0x01;
WRITE_RTC (0x0D,
data,
0x01);
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// data=0x01 clears the RC bit
// Sets the address pointer to Register 0Ch
// Data=0x01 clears the RC bit and keeps C1P=1
// Number of bytes to be written
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A Design Guide to SPI F- AM™ Processor Companion - FM33256B
10.6
SPI Processor Companion Write
/*********PSoC3 Based Pseudo Code for SPI Processor Companion Write **********/
uint8 WRITE_RTC (uint8 addr, uint8 *data_write_ptr, uint8 total_data_count)
{
uint8 i;
// Clear the Transmit Buffer
nvRAM_SPI_1_SPIM_ClearTxBuffer();
// Send Write Enable WREN command
// Make chip select LOW CS = 0
nvRAM_SPI_1_CS_Reg_Write(0);
// Send Write Enable Command WREN
nvRAM_SPI_1_SPIM_WriteTxData(nvRAM_WREN);
// Wait for the transfer to complete
while((nvRAM_SPI_1_SPIM_ReadTxStatus() & nvRAM_SPI_1_SPIM_STS_SPI_DONE) !=
nvRAM_SPI_1_SPIM_STS_SPI_DONE);
// Make chip select High CS = 1
nvRAM_SPI_1_CS_Reg_Write(1);
// Delay
CyDelay(1);
// Clear the Transmit Buffer
nvRAM_SPI_1_SPIM_ClearTxBuffer();
// Make chip select LOW CS = 0
nvRAM_SPI_1_CS_Reg_Write(0);
// Send Processor Companion Write Command
nvRAM_SPI_1_SPIM_WriteTxData(nvRAM_RTC_WRITE_CMD);
// Send Processor Companion Register address
nvRAM_SPI_1_SPIM_WriteTxData((uint8)(addr));
// Wait for the transfer to complete
while((nvRAM_SPI_1_SPIM_ReadTxStatus() & nvRAM_SPI_1_SPIM_STS_SPI_DONE) !=
nvRAM_SPI_1_SPIM_STS_SPI_DONE);
// Send Processor Companion Register data
for(i = 0; i < total_data_count; i++ )
{
nvRAM_SPI_1_SPIM_WriteTxData((uint8)(data_write_ptr[i]));
while((nvRAM_SPI_1_SPIM_ReadTxStatus() & nvRAM_SPI_1_SPIM_STS_SPI_DONE)
!=
nvRAM_SPI_1_SPIM_STS_SPI_DONE);
}
// Make chip select HIGH CS = 1
nvRAM_SPI_1_CS_Reg_Write(1);
}
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A Design Guide to SPI F- AM™ Processor Companion - FM33256B
10.7
SPI Processor Companion Read
/*****************PSoC3 Based Pseudo Code for SPI Processor Companion
Read***************/
uint8 READ_RTC (uint8 addr, uint8 *data_read_ptr, uint8 total_data_count)
{
uint8 i;
// Clear the Transmit Buffer
nvRAM_SPI_1_SPIM_ClearTxBuffer();
// Make chip select LOW CS = 0
nvRAM_SPI_1_CS_Reg_Write(0);
// Send Processor Companion Read Command
nvRAM_SPI_1_SPIM_WriteTxData(nvRAM_RTC_READ_CMD);
// Send Processor Companion Read Register Address
nvRAM_SPI_1_SPIM_WriteTxData((uint8)(addr));
// Wait for the transfer to complete
while((nvRAM_SPI_1_SPIM_ReadTxStatus() & nvRAM_SPI_1_SPIM_STS_SPI_DONE) !=
nvRAM_SPI_1_SPIM_STS_SPI_DONE);
// Read the data and store in data_read_ptr
for(i = 0; i < total_data_count; i++ )
{
// Clear receive buffer
nvRAM_SPI_1_SPIM_ClearRxBuffer();
// Send a dummy byte
nvRAM_SPI_1_SPIM_WriteTxData((uint8)0x00);
// Wait for the transfer to complete
while((nvRAM_SPI_1_SPIM_ReadTxStatus() & nvRAM_SPI_1_SPIM_STS_SPI_DONE)
!=
nvRAM_SPI_1_SPIM_STS_SPI_DONE);
// Wait till the receive buffer has received a byte
while(!nvRAM_SPI_1_SPIM_GetRxBufferSize());
// Copy the read byte to data_read_ptr
data_read_ptr[i] = nvRAM_SPI_1_SPIM_ReadRxData();
}
// Make chip select HIGH CS = 1
nvRAM_SPI_1_CS_Reg_Write(1);
}
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A Design Guide to SPI F- AM™ Processor Companion - FM33256B
Document History
Document Title: AN408 - A Design Guide to SPI F-RAM™ Processor Companion - FM33256B
Document Number: 001-87564
Revision
ECN
Orig. of
Change
Submission
Date
Description of Change
**
4039506
MEDU
06/25/2013
New Spec.
*A
4571568
MEDU
11/17/2014
Added PSoC 3-based User Module project
Replaced Pseudo codes with PSoC 3-based application code.
Rewording / typo fixes
*B
5293268
MEDU
06/02/2016
Added a reference to code example CE204087
Updated template
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Document No. 001-87564 Rev. *B
13
A Design Guide to SPI F- AM™ Processor Companion - FM33256B
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Document No. 001-87564 Rev. *B
14