Operation Of The Wrr (Ram Content Forcible Rewrite) - Renesas M32R/ECU Series User Manual

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14.3.3 Operation of the WRR (RAM Content Forcible Rewrite)

When the WRR (RAM content forcible rewrite) command is issued, the RTD forcibly rewrites the contents of the
internal RAM without causing the CPU's internal bus to stop. Because the RTD writes data to the internal RAM
while there are no transfers performed between the CPU and internal RAM, no extra CPU load is incurred.
Only the 32-bit word-aligned addresses can be specified for read from the internal RAM. (The two low-order
address bits specified by a command are ignored.) Data are written to the internal RAM in 32-bit units.
The external host should transmit the command and address in the first frame and then the write data in the
second frame. The RTD writes to the internal RAM in the third frame after receiving the write data.
a) First frame
(LSB side)
31
RTDRXD
b) Second frame
(LSB side)
31
RTDRXD
b31
Notes: • X = Don't care. (However, if issued immediately after the RCV command, bits 20-31 must all be set to 1.)
• The specified address and write data are transferred LSB-first.
Figure 14.3.4 WRR Command Data Format
The RTD reads out data from the specified address before writing to the internal RAM and again reads out data
from the same address immediately after writing to the internal RAM (this helps to verify the data written to the
internal RAM). The read data is output at the timing shown below.
RTDCLK
RTDRXD
RTDTXD
RTDACK
Notes: • (An) = Specified address
• D(An) = Data at specified address (An)
Figure 14.3.5 Operation of the WRR Command
20 19 18 17 16
X X 0 0 1
Command (WRR)
30
b30
Write data
32 clock 32 clock
periods
WRR(A1) (A1) Write data
3 clock periods
REAL TIME DEBUGGER (RTD)
14.3 Functional Description of the RTD
15 14 13 12
1 0 0 A29 A28
Specified address
32 clock
periods periods
WRR(A2)
D (A1) Read value
before writing
14-6
(MSB side)
1 0
A17 A16
(MSB side)
1 0
b1 b0
32 clock
periods
(A2) Write data
D (A1) Verify value
after writing
32180 Group User's Manual (Rev.1.0)