Serial Communications C ontrollers (SCCs)
MPC8260 PowerQUICC II Family Reference Manual, Rev. 2
20-18 Freescale Semiconductor

Figure 20-9. Output Delay from RTS Asserted for Synchronous Protocols

When RTS is asserted, if CTS is not already asserted, delays to the first data bit depend on when CTS is asserted. Figure 20-10 shows that the delay between CTS and the data can be approximately 0.5 to 1 bit times or no delay, depending on GSMR_H[CTSS].

Figure 20-10. Output Delay from CTS Asserted for Synchronous Protocols

If CTS is programmed to envelope data, negating it during frame transmission causes a CTS lost error. Negating CTS forces RTS high and Tx data to become idle. If GSMR_H[CTSS] is zero, the SCC must sample CTS before a CTS lost is recognized; otherwise, the negation of CTS immediately causes the CTS lost condition. See Figure 20-11.
1. A frame includes opening and closing flags and syncs, if present in the protocol.
TCLK
TXD
Last Bit of Frame DataFirst Bit of Frame Data
NOTE:
(Output)
RTS
(Output)
CTS
(Input)
1. GSMR_H[CTSS] = 0. CTSP is a don’t care.
TCLK
TXD
Last Bit of Frame DataFirst Bit of Frame Data
NOTE:
CTS Sampled Low Here
1. GSMR_H[CTSS] = 1. CTSP is a don’t care.
TCLK
TXD
Last Bit of Frame DataFirst Bit of Frame Data
NOTE:
(Output)
RTS
(Output)
CTS
(Input)
(Output)
RTS
(Output)
CTS
(Input)