Freescale Semiconductor MPC5200B - Manual (Page 525)

MPC5200B Users Guide, Rev. 1
15-14 Freescale Semiconductor
PSC Registers—MBAR + 0x2000, 0x2200, 0x2400, 0x2600, 0x2800, 0x2C00
4:5 00 no action
taken
Causes Tx to stay in current mode.
• If Tx is enabled, it remains enabled.
• If Tx is disabled, it remains disabled.
01 transmitter
enable
Enables operation of Tx channels. SR [TxEMP,TxRDY] sets. If Tx is already
enabled, this command has no effect.
In UART mode, TxRDY and TxEMP bits in SR become asserted.
In Codec mode:
Tx FIFO can be loaded while Tx is disabled, unlike in UART mode. Therefore
this command does not affect TxRDY or URERR behavior. It does not
automatically set TxRDY and URERR. If no data is written to Tx FIFO,
URERR sets at the first
FrameSync after Tx is enabled.
In AC97 mode:
URERR sets if Tx FIFO is empty, Tx is enabled, Rx detects a “Codec Ready”
condition, and a FrameSync occurs before samples are written to the Tx
FIFO.
Note: In Codec / AC97 mode it’s not possible to use the transmitter without the
receiver. To transmit data only, also the receiver must be enabled!
10 transmitter
disable
Terminates Tx operation and clears SR [TxEMP,TxRDY].
• If a character is being sent when Tx is disabled, transmission completes
before Tx becomes inactive.
• If Tx is already disabled, the command has no effect.
In UART mode, SR [TxEMP,TxRDY] are negated.
In Codec mode SR [TxEMP] is negated.
Tx does not clear SR [TxRDY] unless PSC is in remote loop-back or
auto-echo mode. In Codec mode, unlike UART mode, the Tx FIFO may be
loaded while Tx is disabled.
Note: If the transmitter was disabled and transmit data are available in the TX
FIFO, then TX line is not driven low, the frame signal is also visible on the TX line.
11 — Reserved, do not use.
6:7 00 no action
taken
Causes receiver to stay in current mode.
• If receiver is enabled, it remains enabled.
• If receiver is disabled, it remains disabled.
01 receiver
enable
Enables receiver
• If PSC module is not in multidrop mode (MR1[PM]
≠ 11), RECEIVER
ENABLE command enables channel's receiver and forces it into a
search-for-start-bit state. In multidrop mode the Rx continuously monitors the
received data regardless of whether it is enabled or not.
• If receiver is already enabled, this command has no effect.
10 receiver
disable
Immediately disables receiver. In UART mode any character being received is
lost. The command does not affect receiver status bits or other control registers.
• If the PSC module is programmed for local loop-back or multidrop mode, the
receiver operates even though this command is selected.
• If the receiver is already disabled, the command has no effect.
In Codec mode, if the receiver is disabled while a character is being received,
reception completes before the receiver becomes inactive.
11 — Reserved, do not use.
Note: This field selects a single command.
Bit Value Command Description