eCos User Guide
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# Cirrus Logic ARM EP7312 Development Board Hardware Setup

The Cirrus Logic EP7312 Development Board is similar to the EP7212 Development Board from a hardware setup viewpoint, and is based on the same port of eCos.

When rebuilding the RedBoot ROM image or an eCos application, change the "Cirrus Logic processor variant" option (CYGHWR_HAL_ARM_EDB7XXX_VARIANT) from the EP7211 to the EP7312. This can be selected in the eCos Configuration Tool , or if using ecosconfig, can be set by uncommenting the user_value property of this option in ecos.ecc and setting it to "EP7312".

See the RedBoot documentation for building and installing RedBoot for this target. Only RedBoot is supported as a boot image; ROMRAM startup is recommended.

## 90MHz Operation

The EP7xxx targets offer a choice of clock speeds, from 18MHz to a maximum, normally, of 72MHz. These are described as kHz values 18432 36864 49152 and 73728 within the configuration tool. If you have a release which supports it, you will also see 90317 as an available option here, for 90MHz operation.

This option only applies to certain EP7312 hardware, not all EP7312 boards support it. Do not select 90MHz when building RedBoot or your eCos application unless you are absolutely sure that your board supports it.

If you do have a 90MHz board and wish to execute at 90MHz, it is in fact not necessary to build RedBoot specially, if you build your eCos application configured for 90MHz. RedBoot will run at 72MHz and your application will run at 90MHz. If you do install a 90MHz RedBoot, then you must build eCos for 90MHz or timing and baud rates on serial I/O will be wrong.

In other words, code (either eCos app or RedBoot) built for 90MHz will “change up a gear” when it starts up; but code built for 72MHz, because it needs to run correctly on boards without the “gearbox” does not change back down, so if you mix the two, unexpected timing can result. To run a non-eCos application without any hardware initialization code at 90MHz, you must install a specially-built RedBoot.

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