CS22220 Datasheet, PDF (7/34 Pages) Cirrus Logic – WIRELESS PCI/USB CONTROLLER

3.4 Programmable Memory Controller
The CS22220 incorporates a general-purpose memory controller. The memory controller
supports both SDRAM/async SRAM memory interface and a FLASH memory interface.
In the RAM configuration, the system memory interface supports up to 4-Mbyte of 16-bit
SDRAM running at frequency up to 103 MHz (using 133MHz SDRAM) single-state access
cycles or 256KB of 16 bit async SRAM. The memory controller provides programming of
SDRAM parameters such as CAS latency, refresh rate and etc; these registers are located
in miscellaneous configuration registers. The CS22220 memory controller supports the
power saving feature of the SDRAM by toggling the clock enable (CKE) signal. When there
are no pending memory requests from any internal requester, the CS22220 will keep CKE
low to cause the SDRAM to stay in power down mode. Once a memory request is active,
the CS22220 will assert CKE high to cause the SDRAM to come out of power down mode.
Typically, this can reduce memory power consumption by up to 50%.
In ROM configuration, firmware for CS22220 is stored in non-volatile memory and is
accessed through the boot ROM interface. The maximum addressable ROM space
supported is 1MB. ROM read/write and output enable are shared with RAM control pins.
3.5 PCMCIA Interface
The PC-Card interface implemented in Cirrus Logic CS22220 is fully compliant with
PCMCIA 2.1/JEIDA 4.2. The interface supports 16 data bits PCMCIA program I/O and
memory mapped accesses using 11 address bits. PCMCIA interface allows laptop users to
connect to home network to access data and multimedia streams with ease. The interface
provides both memory and I/O access.
The PCMCIA interface incorporates an independent DMA controller to transfer data to/from
the main memory. The ARM has the flexibility in controlling how often it is interrupted and
simplifies the packet transmit/receive protocol. The DMA controller is programmed during
power up.
The CS22220 PCcard interface incorporates a custom mode, which can be used for
embedded applications, by bypassing the standard PC card Pnp configuration
requirements. This interface thus becomes a generic asynchronous 16 bit data interface.
This mode is useful when interfacing the CS22220 wireless network controller directly to an
embedded micro-controller capable of supporting a 16 bit data bus.
CS22220 Wireless PCMCIA Controller
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