45.6.5.7 High-Speed Client Mode
High-speed mode is enabled when a one is written to TWIHS_CR.HSEN. Furthermore, the analog pad filter must be enabled, a one must be written to TWIHS_FILTR.PADFEN and the FILT bit must be cleared. TWIHS High-speed mode operation is similar to TWIHS operation with the following exceptions:
- A host code is received first at normal speed before entering High-speed mode period.
- When TWIHS High-speed mode is active, clock stretching is only allowed after acknowledge (ACK), not-acknowledge (NACK), START (S) or REPEATED START (Sr) (as consequence OVF may happen).
TWIHS High-speed mode allows transfers of up to 3.4 Mbit/s.
The TWIHS client in High-speed mode requires that the peripheral clock runs at a minimum of 14 MHz if client clock stretching is enabled (SCLWSDIS bit at ‘0’). If client clock stretching is disabled (SCLWSDIS bit at ‘1’), the peripheral clock must run at a minimum of 11 MHz (assuming the system has no latency).
Note: When client clock stretching is disabled,
the TWIHS_RHR must always be read before receiving the next data (write access frame
generated by the host). It is strongly recommended to use either the polling method on the
RXRDY flag in TWIHS_SR, or the DMA. If the receive is managed by an
interrupt, the TWIHS interrupt priority must be set to the right level and its latency
minimized to avoid receive overrun.
Note: When client clock stretching is disabled,
the TWIHS_THR must be filled with the first data to send before the beginning of the frame
(read access frame generated by the host). It is strongly recommended to use either the
polling method on the TXRDY flag in TWIHS_SR, or the DMA. If the transmit is managed by an
interrupt, the TWIHS interrupt priority must be set to the right level and its latency
minimized to avoid transmit underrun.