Intel PXA250 and PXA210 External Logic for PCMCIA Implementation, System Memory Interface, 2-11

System Memory Interface

Table 2-8. Variable Latency I/O Interface AC Specifications (Sheet 2 of 2)

				MEMCKLK				Units
Symbol	Description
		99.5	118.0		132.7	147.5	165.9	Notes
tvlioDSW	MD(31:0), DQM(3:0) write data setup to	10	8.5		7.5	6.8	6	ns, 1
	nPWE asserted
tvlioDSWH	MD(31:0), DQM(3:0) write data setup to	20	17		15	13.6	12	ns, 2
	nPWE de-asserted
tvlioDHW	MD(31:0), DQM(3:0) hold after nPWE	10	8.5		7.5	6.8	6	ns, 1
	de-asserted
tvlioDHR	MD(31:0) read data hold after nOE de-	0	0		0	0	0	ns
	asserted
tvlioRDYH	RDY hold after nOE, nPWE de-	0	0		0	0	0	ns
	asserted
tvlioNPWE	nPWE, nOE high time between beats of	20	17		15	13.6	12	ns, 2
	write or read data
NOTES:

1.This number represents 1 MEMCLK period

2.This number represents 2 MEMCLK periods

2.6.5External Logic for PCMCIA Implementation

The PXA250 applications processor requires external glue logic to complete the PCMCIA socket interface. Figure 2-4, “Expansion Card External Logic for a Two-Socket Configuration” on page 2-

12and Figure 2-5, “Expansion Card External Logic for a One-Socket Configuration” on page 2-13show general solutions for one and two socket configurations. Use GPIO or memory-mapped

external registers to control the PCMCIA interface’s reset, power selection (VCC and VPP), and drive enables. These diagrams show the logical connections necessary to support hot insertion capability. For dual-voltage support, level shifting buffers are required for all the applications processor input signals. Hot insertion capability requires each socket be electrically isolated from the other and from the remainder of the memory system. If one or both of these features are not required, you may eliminate some of the logic shown in these diagrams. The applications processor allows either 1-socket or 2-socket solutions. In the 1-socket solution, only minimal glue logic is required (typically for the data transceivers, address buffers, and level shifting buffers.) To achieve this some of the signals are routed through dual-duty GPIO pins. The nOE of the transceivers is driven through the PSKTSEL pin, which is not needed in the one-socket solution. The DIR pin of the transceiver is driven through the RDnWR pin. A GPIO is used for the three-state signal of the address and nPWE lines. These signals are used for memories other than the card interface and must be three-stated.

Note: For 2.5 V VCCN, 5 V to 2.5 V level shifters are required.

Note: PCMCIA is only implemented on the PXA250 applications processor.

In the 2-socket solution, all pins assume their normal duties and glue logic is necessary for proper operation of the system. The pull-ups shown are included for compliance with PC Card Standard - Volume 2 - Electrical Specification. Remove power from these pull-ups during sleep to avoid unnecessary power consumption. Refer to Table 2-9for the PCMCIA or compact Flash card interface AC specifications.

PXA250 and PXA210 Applications Processors Design Guide 2-11