SAM7X128_14 Datasheet, PDF (124/662 Pages) ATMEL Corporation – ARM-based Flash MCU

address field and 1 to the read/write bit. A register is read by scanning its address into the address field and 0 into the
read/write bit, going through the UPDATE-DR TAP state, then scanning out the data.
Refer to the ARM7TDMI reference manuel for more information on Comm channel operations.
Figure 20-5. TAP 8-bit DR Register
TDI
r/w 4 Address 0 31
Data
0
TDO
5
32
Address
Decoder
Debug Comms Control Register
Debug Comms Data Register
A read or write takes place when the TAP controller enters UPDATE-DR state. Refer to the IEEE 1149.1 for more details
on JTAG operations.
 The address of the Debug Comms Control Register is 0x04.
 The address of the Debug Comms Data Register is 0x05.
The Debug Comms Control Register is read-only and allows synchronized handshaking between the processor
and the debugger.
 Bit 1 (W): Denotes whether the programmer can read a data through the Debug Comms Data Register. If
the device is busy W = 0, then the programmer must poll until W = 1.
 Bit 0 (R): Denotes whether the programmer can send data from the Debug Comms Data Register. If R = 1,
data previously placed there through the scan chain has not been collected by the device and so the
programmer must wait.
The write handshake is done by polling the Debug Comms Control Register until the R bit is cleared. Once cleared, data
can be written to the Debug Comms Data Register.
The read handshake is done by polling the Debug Comms Control Register until the W bit is set. Once set, data can be
read in the Debug Comms Data Register.
20.3.4 Device Operations
Several commands on the Flash memory are available. These commands are summarized in Table 20-3 on page 114.
Commands are run by the programmer through the serial interface that is reading and writing the Debug Comms
Registers.
20.3.4.1 Flash Read Command
This command is used to read the Flash contents. The memory map is accessible through this command. Memory is
seen as an array of words (32-bit wide). The read command can start at any valid address in the memory plane. This
address must be word-aligned. The address is automatically incremented.
Table 20-20. Read Command
Read/Write
DR Data
Write
(Number of Words to Read) << 16 | READ
Write
Address
Read
Memory [address]
SAM7X Series [DATASHEET]
6120K–ATARM–11-Feb-14
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