MPC5553/MPC5554 Microcontroller Reference Manual, Rev. 5
19-106
Freescale Semiconductor
19.5.1.1
Initialization of On-Chip ADCs/External Device
The following steps provide an example of configuring the eQADC to initialize the on-chip ADCs and the
external device. In this example, commands will be sent through CFIFO0.
1. Load all required configuration commands in the RAM in such way that they form a queue; this
data structure will be referred below as Queue0.
queue able to configure the on-chip ADCs and external device at the same time.
2. Configure
Section 19.3.2.2, “eQADC Null Message Send Format Register (EQADC_NMSFR)
.”
3. Configure
Section 19.3.2.12, “eQADC SSI Control Register (EQADC_SSICR)
,” to communicate
with the external device.
4. Enable the eQADC SSI by programming the ESSIE field the
Section 19.3.2.1, “eQADC Module
Configuration Register (EQADC_MCR)
a) Write 0b10 to ESSIE field to enable the eQADC SSI. FCK is free running but serial
transmissions are not started.
b) Wait until the external device becomes stable after reset.
c) Write 0b11 to ESSIE field to enable the eQADC SSI to start serial transmissions.
5. Configure the eDMA to transfer data from Queue0 to CFIFO0 in the eQADC.
6. Configure
Section 19.3.2.7, “eQADC Interrupt and eDMA Control Registers 0–5
a) Set CFFS0 to configure the eQADC to generate an eDMA request to load commands from
Queue0 to the CFIFO0.
b) Set CFFE0 to enable the eQADC to generate an eDMA request to transfer commands from
Queue0 to CFIFO0; Command transfers from the RAM to the CFIFO0 will start immediately.
c) Set EOQIE0 to enable the eQADC to generate an interrupt after transferring all of the
commands of Queue0 through CFIFO0.
7. Configure
Section 19.3.2.6, “eQADC CFIFO Control Registers 0–5 (EQADC_CFCRn)
a) Write 0b0001 to the MODE0 field in eQADC_CFCR0 to program CFIFO0 for software
single-scan mode.
b) Write 1 to SSE0 to assert SSS0 and trigger CFIFO0.
8. Because CFIFO0 is in single-scan software mode and it is also the highest priority CFIFO, the
eQADC starts to transfer configuration commands to the on-chip ADCs and to the external
device.
9. When all of the configuration commands have been transferred, EQADC_FISRn[CF0])(see
Section 19.3.2.8) will be set. The eQADC generates a end of queue interrupt. The initialization
procedure is complete.
Figure 19-64. Example of a Command Queue Configuring the On-Chip ADCs/External Device
Configuration Command to ADC0—Ex: Write ADC0_CR
Command Queue in
0x0
0x1
0x2
0x3
System Memory
Configuration Command to ADC2—Ex: Write to external device configuration register
Configuration Command to ADC0—Ex: Write ADC_TSCR
Configuration Command to ADC1—Ex: Write ADC1_CR
Command
Address
Summary of Contents for MPC5553
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