iPod IWIP3G User Guide - Page 168
UART Hardware Flow Control
UPC - 649241862819
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9.6 UART Hardware Flow Control Hardware flow control is enabled by default. It can be disabled by changing the value of PSKEY_UART_CONFIG_XXX (XXX = USR, H4, H5 or BCSP). With iWRAP, the PS key is PSKEY_UART_CONFIG_USR. If PSKEY_UART_CONFIG_USR is 08a8, HW flow control is enabled If PSKEY_UART_CONFIG_USR is 08a0, HW flow control is disabled Hardware flow control can be disabled also with a proper hardware design. If the flow control is enabled from PS-keys, but no flow control is used, the following steps should be implemented in the hardware design: CTS pin must be grounded RTS pin must be left floating WARNING: If hardware flow control is disabled and iWRAP buffers are filled (in command or data mode), the firmware will hang and needs a physical reset to survive. Therefore, hardware flow control should be used whenever possible to avoid this situation. However, if hardware flow control must be disabled, the host system should be designed in a way that it can recognize that the firmware has hung and is able to survive it. 168