Development Support
MPC561/MPC563 Reference Manual, Rev. 1.2
Freescale Semiconductor
23-31
The trap enable control register is not accessed by the CPU, but instead supplies signals to the CPU. The
trap enable bits, VSYNC bit, and the breakpoint bits of this register are loaded from the development port
shift register as the result of trap enable mode transmissions. The trap enable bits are reflected in ICTRL
and LCTRL2 special registers. See
Section 23.6.10, “L-Bus Support Control Register 2
” and
Section 23.6.10, “L-Bus Support Control Register 2
.”
23.4.6.3
Development Port Registers Decode
The development port shift register is selected when the CPU accesses DPIR or DPDR. Accesses to these
two special purpose registers occur in debug mode and appear on the internal bus as an address and the
assertion of an address attribute signal indicating that a special purpose register is being accessed. The
DPIR register is read by the CPU to fetch all instructions when in debug mode and the DPDR register is
read and written to transfer data between the CPU and external development tools. The DPIR and DPDR
are pseudo registers. Decoding either of these registers will cause the development port shift register to be
accessed. The debug mode logic knows whether the CPU is fetching instructions or reading or writing
data. If what the CPU is expecting and what the register receives from the serial port do not match
(instruction instead of data) the mismatch is used to signal a sequence error to the external development
tool.
23.4.6.4
Development Port Serial Communications — Clock Mode Selection
All of the serial transmissions are clock transmissions and are therefore synchronous communications.
However, the transmission clock may be either synchronous or asynchronous with the system clock
(CLKOUT). The development port allows the selection of two methods for clocking the serial
transmissions. The first method allows the transmission to occur without being externally synchronized
with CLKOUT, in this mode a serial clock DSCK must be supplied to the MPC561/MPC563. The other
communication method requires a data to be externally synchronized with CLKOUT.
The first clock mode is called “asynchronous clock” since the input clock (DSCK) is asynchronous with
CLKOUT. To be sure that data on DSDI is sampled correctly, transitions on DSDI must occur a setup time
ahead and a hold time after the rising edge of DSCK. This clock mode allows communications with the
port from a development tool which does not have access to the CLKOUT signal or where the CLKOUT
signal has been delayed or skewed. Refer to the timing diagram in
The second clock mode is called “synchronous self clock”. It does not require an input clock. Instead the
port is timed by the system clock. The DSDI input is required to meet setup and hold time requirements
with respect to CLKOUT rising edge. The data rate for this mode is always the same as the system clock.
Refer to the timing diagram in
.
The selection of clock or self clock mode is made at reset. The state of the DSDI input is latched eight
clocks after SRESET negates. If it is latched low, asynchronous clock mode is enabled. If it is latched high
then synchronous self clock mode is enabled.
Since DSDI is used to select the development port clocking scheme, it is necessary to prevent any
transitions on DSDI during this time from being recognized as the start of a serial transmission. The port
will not begin scanning for the start bit of a serial transmission until 16 clocks after the negation of
SRESET. If DSDI is asserted 16 clocks after SRESET negation, the port will wait until DSDI is negated
to begin scanning for the start bit.
Summary of Contents for MPC561
Page 84: ...MPC561 MPC563 Reference Manual Rev 1 2 lxxxiv Freescale Semiconductor...
Page 144: ...Signal Descriptions MPC561 MPC563 Reference Manual Rev 1 2 2 46 Freescale Semiconductor...
Page 206: ...Central Processing Unit MPC561 MPC563 Reference Manual Rev 1 2 3 62 Freescale Semiconductor...
Page 302: ...Reset MPC561 MPC563 Reference Manual Rev 1 2 7 14 Freescale Semiconductor...
Page 854: ...Time Processor Unit 3 MPC561 MPC563 Reference Manual Rev 1 2 19 24 Freescale Semiconductor...
Page 968: ...Development Support MPC561 MPC563 Reference Manual Rev 1 2 23 54 Freescale Semiconductor...
Page 1144: ...Internal Memory Map MPC561 MPC563 Reference Manual Rev 1 2 B 34 Freescale Semiconductor...
Page 1212: ...TPU3 ROM Functions MPC561 MPC563 Reference Manual Rev 1 2 D 60 Freescale Semiconductor...
Page 1216: ...Memory Access Timing MPC561 MPC563 Reference Manual Rev 1 2 E 4 Freescale Semiconductor...