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NXP Semiconductors
PNX15xx/952x Series
Volume 1 of 1
Chapter 8: General Purpose Input Output Pins
PNX15XX_PNX952X_SER_N_4
NXP B.V. 2007. All rights reserved.
Product data sheet
Rev. 4.0 — 03 December 2007
8-280
queue, 16 2-bit samples if 2 outputs are being driven by the FIFO queue or 8 4-bit
samples if 4 outputs are being driven by the FIFO queue. This is illustrated in
Remark: The number of samples to be generated is specified in a multiple of 32-bit
word being sent by the GPIO module. Therefore, there is no fine-grain way to specify
the exact amount of samples to be sent.
Additional GPIO Pattern Generation Feature: Timestamp Signal Generation
In pattern generation modes the GPIO can be programmed to generate events which
signal that the last 32-bit word read from a DMA buffer has arrived at a GPIO output
pin.
The event will be a positive edge pulse with the duration of the event to be greater
than or equal to 148 ns (2 x [1/13.5 MHz]). The specic event generated for each
FIFO queue is LAST_WORD.
LAST_WORD[3:0] have the same properties as the other internal signals as
The generation of the LAST_WORD[3:0] internal signals is enabled by setting the
EN_EV_TSTAMP eld of the relevant GPIO_EV[3:0] register.
2.4 GPIO Error Behaviour
A DMA buffer overrun, FIFO_OE, occurs if a new DMA buffer is not supplied by
software in time, i.e if BUF1_RDY and BUF2_RDY are both active.
Similarly to the software double DMA buffering scheme, the GPIO module also
implements a double internal buffering scheme per FIFO. This double buffering
scheme allows to hide the latency of the accesses to the system memory. Each
internal buffer is composed of an internal 64-byte memory. In sampling mode, the
GPIO uses one of the internal 64-byte memories to store the being sampled data
while the second 64-byte memory is being stored into memory. In pattern generation
mode, the 64-byte memories are used in the opposite direction. In both cases the
Figure 7:
Up to 4-bit Samples per FIFO in Pattern Generation Mode
31302928272625242322212019181716151413121110 98 7 6 5 4 3210
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
0
1
2
3
4
5
6
7
31
0
31
0
31
0
IO_SEL_0 sample
IO_SEL_1 sample IO_SEL_0 sample
IO_SEL_3 sample IO_SEL_2 sample IO_SEL_1 sample IO_SEL_0 sample
31
30
31
30
29
28
1-bit shifted out
2-bit shifted out
4-bits shifted out
=> 32 samples
=> 16 samples
=> 8 samples