Enhanced Serial Communication Interface (eSCI)
MPC5510 Microcontroller Family Reference Manual, Rev. 1
24-30
Freescale Semiconductor
Preliminary
Figure 24-21. 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 (ESCI
x
_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. The TXDIR bit
determines whether the TXD pin is going to be used as an input (TXDIR=0) or an output (TXDIR=1) in
the single-wire mode of operation.
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_PCR
nn
[ODE] = 1). Weak pullup
may optionally be enabled if the external transmitting device is also open drain. See
Configuration Registers (SIU_PCR)
During transmission, the transmitter must be enabled (TE=1); the receiver may be enabled or disabled. If
the receiver is enabled (RE=1), transmissions will be echoed back on the receiver. Set or clear open drain
output enable depending on desired operation.
24.4.6
Loop Operation
In loop operation, the transmitter output goes to the receiver input. The RXD signal is disconnected from
the eSCI.
Figure 24-22. Loop Operation (LOOPS = 1, RSRC = 0)
Enable loop operation by setting the LOOPS bit and clearing the RSRC bit in eSCI control register 1
(ESCI
x
_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).
24.4.7
Disabling the eSCI
Each of the eSCI modules can be independently disabled by setting ESCI
x
_CR2[MDIS] = 1. Disabling the
module turns off the clock to the module, although some of the module registers may be accessed by the
Transmitter
Receiver
TXD
TXD input signal
TXD output signal
RXD
Transmitter
Receiver
TXD
TXD output signal
RXD