STMicroelectronics SPC572L series Reference Manual page 1272

LVDS Fast Asynchronous Serial Transmission (LFAST) – Interprocessor Communications
47.7.6.2.1.1 Programing model for unsolicited frame transmit
1. Program MCR[TXEN] = 1 and MCR[DRFEN] = 1 in the Mode Configuration Register
(MCR) to enable the Tx path.
2. Select the desired clock rate at which data should be transmitted, using ICLC transfers
and appropriate programing of SCR[TDR].
3. Read the UNSTCR[USNDRQ].
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4. UNSTCR[USNDRQ] is cleared by the Tx Block after the frame transfer.
5. TISR[TXUNSF] = 1 when the frame is transmitted.
6. CTS is set depending on the Push-Pull mode setting defined by MCR[CTSEN].
47.7.6.2.2 Unsolicited frame receive flow
Whenever an Unsolicited frame is received from the peer device, the following steps are
performed:
If UNSRSR[URXDV] = 0 then:
1. The payload size field of the header is first saved into the UNSRSR[URPCNT].
2. The payload is stored in the UNSTDR0–UNSTDR8.
3. UNSRSR[URXDV] = 1 and the RISR[RXUNSF] = 1 indicating the successful reception
of the frame.
If UNSRSR[URXDV] = 1 then:
1. The current unsolicited frame is ignored.
2. RISR[RXUOF] = 1.
Typical steps by the processor after RISR[RXUNSF] = 1 is as follows:
1. The processor reads UNSRSR to get the payload size of the frame.
2. It then reads the complete frame by reading UNSRDR8–UNSRDR0 for the payload
size as received in the frame.
3. Then it clears the interrupt (write RISR[RXUNSF] = 1) and also the UNSRSR[URXDV]
bit.
47.7.6.3 ICLC flow
The ICLC (Interface Control Logical Channel) is defined as a separate logical channel type,
which is mainly meant for implementing the data rate change in the LFAST interface and
initiating the test modes.
47.7.6.3.1 ICLC data transmit flow
Whenever the processor intends to transfer an ICLC frame to the LFAST slave then the
following steps are to be followed.
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If UNSTCR[USNDRQ] = 1 then wait for either of the following:
– UNSTCR[USNDRQ] = 0
– TISR[TXUNSF] = 1.
If UNSTCR[USNDRQ] = 0 then:
– Program the unsolicited payload in UNSTDR0–UNSTDR8, and can be
written up to a payload of frame of a maximum of 288 bits.
– Program the unsolicited frame header in UNSTCR[UNSHDR].
– Program UNSTCR[USNDRQ] = 1.
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