Enhanced Queued Analog-to-Digital Converter (eQADC)
MPC5510 Microcontroller Family Reference Manual, Rev. 1
Freescale Semiconductor
31-41
Preliminary
31.4.2
Command/Result Queues
The command and result queues are actually part of the eQADC system although they are not hardware
implemented inside the eQADC. Instead command and result queues are user-defined queues located in
system memory. Each command queue entry is a 32-bit command message.The last entry of a command
queue has the EOQ bit asserted to indicate that it is the last entry of the queue. The result queue entry is a
16-bit data item.
Section 31.1.3, “Modes of Operation
for a description of the message formats and their flow in
eQADC.
Refer to
Section 31.5.5, “Command Queue and Result Queue Usage
,” for examples of how command
queues and result queues can be used.
31.4.3
eQADC Command FIFOs
31.4.3.1
CFIFO Basic Functionality
There are six prioritized CFIFOs located in the eQADC. Each CFIFO is four entries deep, and each CFIFO
entry is 32 bits long. A CFIFO serves as a temporary storage location for the command messages stored
in the command queues in system memory. When a CFIFO is not full, the eQADC sets the corresponding
CFFF bit in
Section 31.3.3.8, “eQADC FIFO and Interrupt Status Registers 0–5 (EQADC_FISRn)
.” If
Section 31.3.3.7, “eQADC Interrupt and eDMA Control Registers 0–5
,” the eQADC generates requests for more commands from a command queue. An
interrupt request, served by the host CPU, is generated when CFFS is negated, and a eDMA request, served
by the eDMA, is generated when CFFS is asserted. The host CPU or the eDMA respond to these requests
Table 31-31. Correspondence between Analog Voltages and Digital Values
1, 2
1
V
REF
=V
RH
-V
RL
=5.12V. Resulting in one 12-bit count (lsb) =1.25mV.
2
The two’s complement representation is used to express negative values.
Voltage Level on
Channel
(V)
Corresponding 12-bit
Conversion Result
Returned by the ADC
16-bit Result
Sent to RFIFOs
(FMT=0)
3
3
Assuming uncalibrated conversion results.
16-bit Result
Sent to RFIFOs
(FMT=1)
Single-Ended
Conversions
5.12
0xFFF
0x3FFC
0x1FFC
5.12 – lsb
0xFFF
0x3FFC
0x1FFC
...
...
...
...
2.56
0x800
0x2000
0x0000
...
...
...
...
1 lsb
0x001
0x0004
0xE004
0
0x000
0x0000
0xE000