SAB82538 Datasheet, PDF (76/253 Pages) Infineon Technologies AG – ICs for Communications

SAB 82538
SAF 82538
A received character is considered to be recognized as a valid XON or XOFF character
– if it is correctly framed (correct length),
– if its bits match the ones in the XON or XOFF registers over the programmed character
length,
– if it has correct parity (if applicable).
Received XON and XOFF characters are always stored in the receive FIFO, as any
other characters.
In-Band Flow Control of Transmitted Characters
Recognition of an XON or an XOFF character causes always a corresponding maskable
interrupt status to be generated (ISR1.XON / IMR1.XON; ISR1.XOFF / IMR1.XOFF).
Further action depends on the setting of a control bit MODE.FLON (Flow Control On):
0 No further action is automatically taken by the ESCC8.
1 The reception of an XOFF character automatically turns off the transmitter after the
currently transmitted character (if any) has been completely shifted out (XOFF state).
The reception of an XON character automatically makes the transmitter resume
transmitting (XON state).
After hardware RESET, bit MODE.FLON is at “0”.
When bit MODE.FLON is made to go from “0” to “1”, the transmitter is first in the “XON
state”, until an XOFF character is received.
When bit MODE.FLON is made to go from “1” to “0”, the transmitter always goes in the
“XON state”, and transmission is only controlled by the user and by the CTS input.
The in-band flow control of the transmitter via received XON and XOFF characters can
be combined with control via CTS pin, i.e. the effect of the CTS pin is independent of
whether in-band control is used or not. The transmitter is enabled only if CTS is low and
XON state has been reached.
Transmitter Status Bit
The status bit “Flow Control Status” (STAR.FCS) indicates the current state of the
transmitter, as follows:
0 if the transmitter is in XON state
1 if the transmitter is in XOFF state
Note: The transmitter cannot be turned off by software without disrupting data possibly
remaining in the XFIFO.
Semiconductor Group
76