Enhanced Serial Communication Interface (eSCI)
MPC5566 Microcontroller Reference Manual, Rev. 2
21-32 Freescale Semiconductor
Figure 21-21. Single-Wire Operation (LOOPS = 1, RSRC = 1)
Enable single-wire operation by setting the LOOPS bit and the receiver source bit, RSRC, in eSCI control
register 1 (ESCIx_CR1). Setting the LOOPS bit disables the path from the RXD signal to the receiver.
Setting the RSRC bit connects the receiver input to the output of the TXD pin driver.
During reception, both the transmitter and receiver must be enabled (TE = 1 and RE = 1). The
SIU_PCR89[PA] and SIU_PCR91[PA] bits must be set to select the TXD function for the relevant eSCI
module, and the TXD pin should be set for open drain operation (SIU_PCRnn[ODE] = 1). Optionally, if
the external transmitting device is also open drain, a weak pullup can be enabled.
Refer to Section 6.3.1.12, “Pad Configuration Registers (SIU_PCR)”.
During transmission, the transmitter must be enabled (TE = 1); the receiver can be enabled or disabled. If
the receiver is enabled (RE = 1), transmissions are echoed back on the receiver. Set or clear open drain
output enable depending on desired operation.
21.4.7 Loop Operation
In loop operation the transmitter output goes to the receiver input. The RXD signal is disconnected from
the eSCI.
Figure 21-22. Loop Operation (LOOPS = 1, RSRC = 0)
Enable loop operation by setting the LOOPS bit and clearing the RSRC bit in eSCI control register 1
(ESCIx_CR1). Setting the LOOPS bit disables the path from the RXD signal to the receiver. Clearing the
RSRC bit connects the transmitter output to the receiver input. Both the transmitter and receiver must be
enabled (TE = 1 and RE = 1).
21.4.8 Modes of Operation
21.4.8.1 Run Mode
Run mode is the normal operating mode.
Transmitter
Receiver
TXD
TXD input signal
TXD output signal
RXD
Transmitter
Receiver
TXD
TXD output signal
RXD
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