SAM7S256_14 Datasheet, PDF (127/775 Pages) ATMEL Corporation – ARM-based Flash MCU

20.2.3 Entering Programming Mode
The following algorithm puts the device in Parallel Programming Mode:
• Apply GND, VDDIO, VDDCORE, VDDFLASH and VDDPLL.
• Apply XIN clock within T_{POR_RESET} if an external clock is available.
• Wait for T_{POR_RESET}
• Start a read or write handshaking.
Note:
After reset, the device is clocked by the internal RC oscillator. Before clearing RDY signal, if an external clock (> 32
kHz) is connected to XIN, then the device switches on the external clock. Else, XIN input is not considered. A higher
frequency on XIN speeds up the programmer handshake.
20.2.4 Programmer Handshaking
An handshake is defined for read and write operations. When the device is ready to start a new operation (RDY
signal set), the programmer starts the handshake by clearing the NCMD signal. The handshaking is achieved once
NCMD signal is high and RDY is high.
20.2.4.1 Write Handshaking
For details on the write handshaking sequence, refer to Figure 20-3, Figure 20-4 and Table 20-4.
Figure 20-3. SAM7S512/256/128/64/321/161Parallel Programming Timing, Write Sequence
NCMD
RDY
NOE
NVALID
2
3
4
5
DATA[15:0]
1
MODE[3:0]
Figure 20-4. SAM7S32/16 Parallel Programming Timing, Write Sequence
NCMD
RDY
NOE
NVALID
2
3
DATA[7:0]
1
MODE[3:0]
4
5
SAM7S Series [DATASHEET]
6175M–ATARM–26-Oct-12
127