Memory Controller

Figure 6-30. 16-Bit PC Card I/O 16-Bit Access to 8-Bit Device

0ns

MEMCLK MA[25:1],nPREG,PSKTSEL MA[0] nPCE2 nPCE1

IOx_SET

nPIOW,nPIOR RDnWR nIOIS16

100ns

IOx_SET

IOx_HOLD

IOx_ASST_HOLD

200ns

300ns

 

 

 

 

 

 

 

 

 

 

 

 

IOx_HOLD

IOx_ASST_HOLD

nPWAIT read_data

IOx_ASST_WAIT + wait states IOx_ASST_WAIT + wait states

write_data

Low Byte

High Byte

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).

6.9Companion 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 6-31and Figure 6-32.

6-70

Intel® PXA255 Processor Developer’s Manual

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Intel PXA255 manual Companion Chip Interface, Bit PC Card I/O 16-Bit Access to 8-Bit Device