Transmit Clock Source Bit (Tcm) Sccr Bit 15; Sci Data Registers; Figure 8-8 Sci Programming Model - Data Registers - Motorola DSP56305 User Manual

Serial Communication Interface (SCI)
SCI Programming Model
8.3.3.5

Transmit Clock Source Bit (TCM) SCCR Bit 15

TCM selects whether an internal or external clock is used for the transmitter. If TCM is
cleared, the internal clock is used. If TCM is set, the external clock (from the SCLK
signal) is used. Hardware and software reset clear TCM.
8.3.4

SCI Data Registers

The SCI data registers are divided into two groups: receive and transmit (see Figure 8-8).
There are two receive registers—a Receive Data Register (SRX) and a serial-to-parallel
Receive Shift Register. There are also two transmit registers—a Transmit Data Register
(called either STX or STXA) and a parallel-to-serial Transmit Shift Register.
23 16
SRXH
RXD
Note: SRX is the same register decoded at three different addresses.
23 16
STXH
SCI Transmit Data Shift Register
23 16
Note: 1. Bytes are masked on the fly.
2. STX is the same register decoded at four different addresses.

Figure 8-8 SCI Programming Model - Data Registers

8-20
15 8 7
SRXM
SCI Receive Data Shift Register
(a) Receive Data Register
15 8 7
STXM
15 8 7
(b) Transmit Data Register
DSP56305 User's Manual
0
SCI Receive Data Register High (Read Only)
SCI Receive Data Register Middle (Read Only)
SRXL
SCI Receive Data Register Low (Read Only)
0
SCI Transmit Data Register High (Write Only)
SCI Transmit Data Register Middle (Write Only)
STXL
SCI Transmit Data Register Low (Write Only)
TXD
0
SCI Transmit Data Address Register (Write Only)
STXA
AA0694
MOTOROLA