6-70
Intel® PXA255 Processor
Developer’s Manual
Memory Controller
The interface waits the smallest possible amount of time (x_ASST_WAIT) before it checks the
value of the nPWAIT signal. If the nPWAIT signal is asserted (active low), the interface continues
to wait (for a variable number of wait states) until nPWAIT is deasserted. When the nPWAIT signal
is deasserted, the command continues to be asserted for a fixed amount of time (x_ASST_HOLD).
6.9
Companion Chip Interface
The processor can be connected to a companion chip in two different ways:
•
Alternate Bus Master Mode
•
Variable Latency I/O (See
Section 6.7.6
)
The connection methods are illustrated in
Figure 6-31
and
Figure 6-32
.
Figure 6-30. 16-Bit PC Card I/O 16-Bit Access to 8-Bit Device
Low Byte
High Byte
IOx_ASST_HOLD
IOx_ASS wait states
IOx_ASST_HOLD
IOx_ASS wait states
IOx_HOLD
IOx_SET
IOx_HOLD
IOx_SET
0ns
100ns
200ns
300ns
MEMCLK
MA[25:1],nPREG,PSKTSEL
MA[0]
nPCE2
nPCE1
nPIOW,nPIOR
RDnWR
nIOIS16
nPWAIT
read_data
write_data
Содержание PXA255
Страница 1: ...Intel PXA255 Processor Developer s Manual January 2004 Order Number 278693 002 ...
Страница 24: ...xxiv Intel PXA255 Processor Developer s Manual Contents ...
Страница 30: ...1 6 Intel PXA255 Processor Developer s Manual Introduction ...
Страница 310: ...7 46 Intel PXA255 Processor Developer s Manual LCD Controller ...
Страница 330: ...8 20 Intel PXA255 Processor Developer s Manual Synchronous Serial Port Controller ...
Страница 358: ...9 28 Intel PXA255 Processor Developer s Manual I2 C Bus Interface Unit ...
Страница 488: ...13 36 Intel PXA255 Processor Developer s Manual AC 97 Controller Unit ...
Страница 572: ...16 30 Intel PXA255 Processor Developer s Manual Network SSP Serial Port ...
Страница 599: ...Intel PXA255 Processor Developer s Manual 17 27 Hardware UART ...
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