Bluegiga IWIP3G - IWRAP - IPHONE 3G, Руководство пользователя

Страница: 168 / 211

168
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.