peb20525 Infineon Technologies Corporation, peb20525 Datasheet - Page 77

• Manufacturer Part Number: peb20525
• Description: 2 Channel Serial Optimized Communication Controller For Hdlc/ppp
• Manufacturer: Infineon Technologies Corporation

3.2.14
3.2.14.1 RTS/CTS Handshaking
The SCC provides two pins (RTS, CTS) per serial channel supporting the standard
request-to-send modem handshaking procedure for transmission control.
A transmit request will be indicated by outputting logical ‘0’ on the request-to-send output
(RTS). It is also possible to control the RTS output by software. After having received the
permission to transmit (CTS) the SCC starts data transmission.
In the case where permission to transmit is withdrawn in the course of transmission, the
frame is aborted and IDLE is sent. After transmission is enabled again by re-activation
of CTS, and if the beginning of the frame is still available in the SCC, the frame will be
re-transmitted (self-recovery). However, if the permission to transmit is withdrawn after
the data available in the shadow part of the SCC transmit FIFO has been completely
transmitted and the pool is released, the transmitter and the SCC transmit FIFO are
reset, the RTS output is deactivated and an interrupt (XMR) is generated.
Note: For correct identification as to which frame is aborted and thus has to be repeated
Note: In the case where permission to transmit is not required, the CTS input can be
Additionally, any transition on the CTS input pin, sampled with the transmit clock, will
generate an interrupt indicated via register ISR1, if this function is enabled by setting the
’CSC’ bit in register
Data Sheet
after an XMR interrupt has occurred, the contents of SCC transmit FIFO have to
be unique, i.e. SCC transmit FIFO should not contain data of more than one frame,
which could happen if transmission of a new frame is started by providing new
data to the transmitter too early. For this purpose the ’All Sent’ interrupt
(ISR1.ALLS) has to be waited for before providing new transmit data.
connected directly to
Modem Control Signals (RTS, CTS, CD)
IMR1
to ’0’.
V
SS
and/or bit ’FCTS’ (register CCR1H) may be set to ’1’.
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Functional Overview
PEB 20525
PEF 20525
2000-09-14