MC68HC908GR16 Datasheet, PDF (167/310 Pages) Motorola, Inc – Microcontrollers

Freescale Semiconductor, Inc.
Enhanced Serial Communications Interface (ESCI) Module
Functional Description
When queueing an idle character, return the TE bit to logic 1 before the stop bit of
the current character shifts out to the TxD pin. Setting TE after the stop bit appears
on TxD causes data previously written to the SCDR to be lost. A good time to toggle
the TE bit for a queued idle character is when the SCTE bit becomes set and just
before writing the next byte to the SCDR.
14.4.2.5 Inversion of Transmitted Output
The transmit inversion bit (TXINV) in ESCI control register 1 (SCC1) reverses
the polarity of transmitted data. All transmitted values including idle, break, start,
and stop bits, are inverted when TXINV is at logic 1. See 14.8.1 ESCI Control
Register 1.
14.4.2.6 Transmitter Interrupts
These conditions can generate CPU interrupt requests from the ESCI transmitter:
• ESCI transmitter empty (SCTE) — The SCTE bit in SCS1 indicates that the
SCDR has transferred a character to the transmit shift register. SCTE can
generate a transmitter CPU interrupt request. Setting the ESCI transmit
interrupt enable bit, SCTIE, in SCC2 enables the SCTE bit to generate
transmitter CPU interrupt requests.
• Transmission complete (TC) — The TC bit in SCS1 indicates that the
transmit shift register and the SCDR are empty and that no break or idle
character has been generated. The transmission complete interrupt enable
bit, TCIE, in SCC2 enables the TC bit to generate transmitter CPU interrupt
requests.
14.4.3 Receiver
Figure 14-6 shows the structure of the ESCI receiver. The receiver I/O registers
are summarized in Figure 14-3.
14.4.3.1 Character Length
The receiver can accommodate either 8-bit or 9-bit data. The state of the M bit in
ESCI control register 1 (SCC1) determines character length. When receiving 9-bit
data, bit R8 in ESCI control register 3 (SCC3) is the ninth bit (bit 8). When receiving
8-bit data, bit R8 is a copy of the eighth bit (bit 7).
MC68HC908GR16 — Rev. 1.0
MOTOROLA
Enhanced Serial Communications Interface (ESCI) Module
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Data Sheet
167