AN2074 Freescale Semiconductor / Motorola, AN2074 Datasheet - Page 19

• Manufacturer Part Number: AN2074
• Description: DSP56300 JTAG Examples
• Manufacturer: Freescale Semiconductor / Motorola

3.2.2 JTAG_EXECUTE Subroutine
JTAG_EXECUTE:
read_TDO
TDO_SET
TDO_CLR
shift
no_read_TDO
TMS_SET
TMS_CLR
cont1
TDI_SET
TDI_CLR
cont2
done
3.3 BYPASS Example
The JTAG_EXECUTE subroutine performs the operations necessary to emulate the JTAG/OnCE
operation. When the JTAG_RTI sends an 8-bit item of data, the JTAG_EXECUTE first determines if bit 2
is set to indicate that
Next, the JTAG_EXECUTE subroutine determines the value of bit 5 and sets or clears the
accordingly. Then, the subroutine determines the value of bit 4 and sets or clears
The
until an exit value of $00 is encountered. The
x:JTAG_OUT.
The BYPASS example shows how this instruction is executed. The Select-IR scan path is selected to shift
in the BYPASS instruction by sending 1111 on
the data $c0ffee on
move
tst
beq
move
brclr
brclr
move
bra
move
lsr
ror
brclr
bset
bra
bclr
brclr
bset
bra
bclr
bset
rep
nop
bclr
bra
move
clr
rts
TCK
signal is then toggled to send the values to the target DSP. The JTAG_EXECUTE routine repeats
x:(r0)+,a1
a
done
a1,x:JTAG_INSTR
#DATA_RD,x:JTAG_INSTR,no_read_TDO
#TDO_BIT,x:M_PDRD,TDO_CLR
#>1,a
shift
#>0,a
a
b
#DATA_TMS,x:JTAG_INSTR,TMS_CLR
#TMS_BIT,x:M_PDRD
>cont1
#TMS_BIT,x:M_PDRD
#DATA_TDI,x:JTAG_INSTR,TDI_CLR
#TDI_BIT,x:M_PDRD
>cont2
#TDI_BIT,x:M_PDRD
#TCK_BIT,x:M_PDRD
#3
#TCK_BIT,x:M_PDRD
>JTAG_EXECUTE
b1,x:JTAG_OUT
b
TDO
TDI
Freescale Semiconductor, Inc.
. Since the BYPASS instruction allows serial data to be transferred from
For More Information On This Product,
needs to be read. The data shifted out on
Example 10. JTAG Bit-Banging Routine
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DSP56300 JTAG Examples
TDO
TDI
. Next, the Select-DR scan path is selected to shift in
output is stored in internal memory location
TDO
is shifted into accumulator b.
TDI
value accordingly.
BYPASS Example
TMS
value
TDI
to
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