参数资料
型号: HSP50214BVIZ
厂商: Intersil
文件页数: 39/62页
文件大小: 0K
描述: IC DOWNCONVERTER 14BIT 120-MQFP
标准包装: 24
功能: 降频器
RF 型: AMPS,CDMA,GSM,TDMA
封装/外壳: 120-BQFP
包装: 托盘
HSP50214B
Figure 37 shows the interface between a 16-bit
microprocessor (or other baseband processing engine) and
the Buffer RAM Output Section of the Programmable Down
INTRRP
8 CLKS
> 4 CLKS
Converter, configured for data output via the parallel outputs
AOUT and BOUT. In the 16-bit microprocessor interface
configuration, the Buffer RAM pointer is incremented when
OEAL,
OEBL
the μ Processor reads address SEL(2:0) = 7 and OEBL = 0.
After reset, the FIFO must be incremented to read the first
SEL(0:2)
AOUT(7:0),
0
I
1
Q
4
FR
7
0
I
1
Q
sample set. This is because the RAM read and write pointers
BOUT(7:0)
cannot point to the same address. Thus, the FIFO pointer
must move to the next address before reading the next set of
data (I, Q, |r|, φ , and f ) samples. 4 PROCCLK cycles are
required after an increment before reading can resume. The
PROCCLK
1 2 3 4 5 6 7 8
1 2 3 4
FIFO write pointer is reset to zero (the first data sample) when
Control Word 22 is written to via the 8-bit microprocessor
interface. See the Microprocessor Read Section for more
detail on how to obtain the Buffer RAM output with this
technique. Figure 39 shows the timing diagram required for
parallel output operations. In this diagram, only the I, Q and
Frequency data are taken from each sample before
incrementing to the next sample. Figure 39 assumes that the
pointer has already been incremented into a sample.
NOTE: For the very first sample read, the pointer must be
incremented first and 4 PROCCLKs must pass before
this sample can be read.
Figure 38 shows INTRRP going low before the FIFO is read.
The FIFO can be read before the number of samples
reaches the INTRRP pointer. The number of samples in the
FIFO must be monitored by the user via a status read.
FIGURE 39. TIMING DIAGRAM FOR PDC IN FIFO MODE WITH
OUTPUTS I, Q, AND FREQUENCY SENT TO
AOUT(7:0) AND BOUT(7:0)
Suppose the depth of the Buffer RAM Output Section is
programmed for an INTRRP pointer depth of 4. If the output
is at 4 times the baud rate, the processing routine for the
microprocessor may only need to read the buffer when the
Buffer RAM had 4 samples since processing is usually on a
baud by baud basis.
Figure 39 illustrates the conceptual view of the FIFO as a
circular buffer, with the Write address one step ahead of the
Read Address.
Figure 40A deals with clockwise read and write address
incrementing. The FIFO depth is the difference between the
Write and Read pointers, modulo 8. Figure 40B illustrates a
FIFO status of Full, while Figure 40C illustrates a FIFO
empty status condition. Figure 40D illustrates a programmed
PDC
INTRRP
OEAL
AOUT(7:0)
OEBL
BOUT(7:0)
SEL(2:0)
INT
RD
D(15:8)
16-BIT
μ P
D(7:0)
A(2:0)
FIFO depth of 3 and the INTRRP signal indicating that the
buffer has sufficient data to be read.
Following some simple rules for operating the FIFO will
eliminate most operational errors:
Rule #1: The Read and Write Pointers cannot point at the
same address (the circuitry will not allow this).
Rule #2: The FIFO is full when the Write Address = Read
Address -1 (no more data will be written until some samples
are read or the FIFO is reset).
Rule #3: The FIFO is empty when the Read Address =
FIGURE 38. INTERFACE BETWEEN A 16-BIT
MICROPROCESSOR AND PDC IN FIFO BUFFER
39
(Write Address -1) (the circuitry will not allow the read
pointer to be incremented).
Rule #4: You cannot write over what you have not read.
Rule #5: RESET places the Write address pointer = 000 and
Read address pointer = 111.
Rule #6: The best addressing scheme is to read the FIFO
until it is empty. This avoids erroneous INTRRP assertions
and provides for simple FIFO depth monitoring. The interrupt
is generated when the depth increments past the threshold.
FN4450.4
May 1, 2007
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