PRELIMINARY
CYW43438
Figure 19. Startup Signaling Sequence
LPO
Host IOs unconfigured
Host IOs configured
VDDIO
T1
HostResetX
BT_GPIO_0
(BT_DEV_WAKE)
T2
BTH IOs unconfiguredBTH IOs configured
BT_REG_ON
BT_GPIO_1
(BT_HOST_WAKE)
T3
Host side drives
this line low
BT_UART_CTS_N
BT_UART_RTS_N
BTH device drives this
line low indicating
transport is ready
T4
CLK_REQ_OUT
Notes :
T5
Driven
Pulled
T1 is the time for host to settle it’s IOs after a reset.
T2 is the time for host to drive BT_REG_ON high after the Host IOs are configured.
T3 is the time for BTH (Bluetooth) device to settle its IOs after a reset and reference clock settling time has
elapsed.
T4 is the time for BTH device to drive BT_UART_RTS_N low after the host drives BT_UART_CTS_N low. This
assumes the BTH device has already completed initialization.
T5 is the time for BTH device to drive CLK_REQ_OUT high after BT_REG_ON goes high. Note this pin is used for
designs that use an external reference clock source from the Host. This pin is irrelevant for Crystal reference
clock based designs where the BTH device generates it’s own reference clock from an external crystal connected
to it’s oscillator circuit.
Timing diagram assumes VBAT is present.
Document Number: 002-14796 Rev. *K
Page 36 of 101
CYPRESS [ CYPRESS ]
