Datasheet

323
ATmega640/V-1280/V-1281/V-2560/V-2561/V [DATASHEET]
2549Q–AVR–02/2014
29.7 Register Description
29.7.1 SPMCSR – Store Program Memory Control and Status Register
The Store Program Memory Control and Status Register contains the control bits needed to control the Boot
Loader operations.
• Bit 7 – SPMIE: SPM Interrupt Enable
When the SPMIE bit is written to one, and the I-bit in the Status Register is set (one), the SPM ready interrupt will
be enabled. The SPM ready Interrupt will be executed as long as the SPMEN bit in the SPMCSR Register is
cleared.
• Bit 6 – RWWSB: Read-While-Write Section Busy
When a Self-Programming (Page Erase or Page Write) operation to the RWW section is initiated, the RWWSB will
be set (one) by hardware. When the RWWSB bit is set, the RWW section cannot be accessed. The RWWSB bit
will be cleared if the RWWSRE bit is written to one after a Self-Programming operation is completed. Alternatively
the RWWSB bit will automatically be cleared if a page load operation is initiated.
• Bit 5 – SIGRD: Signature Row Read
If this bit is written to one at the same time as SPMEN, the next LPM instruction within three clock cycles will read
a byte from the signature row into the destination register. see “Reading the Signature Row from Software” on
page 317 for details. An SPM instruction within four cycles after SIGRD and SPMEN are set will have no effect.
This operation is reserved for future use and should not be used.
• Bit 4 – RWWSRE: Read-While-Write Section Read Enable
When programming (Page Erase or Page Write) to the RWW section, the RWW section is blocked for reading (the
RWWSB will be set by hardware). To re-enable the RWW section, the user software must wait until the program-
ming is completed (SPMEN will be cleared). Then, if the RWWSRE bit is written to one at the same time as
SPMEN, the next SPM instruction within four clock cycles re-enables the RWW section. The RWW section cannot
be re-enabled while the Flash is busy with a Page Erase or a Page Write (SPMEN is set). If the RWWSRE bit is
written while the Flash is being loaded, the Flash load operation will abort and the data loaded will be lost.
• Bit 3 – BLBSET: Boot Lock Bit Set
If this bit is written to one at the same time as SPMEN, the next SPM instruction within four clock cycles sets Boot
Lock bits, according to the data in R0. The data in R1 and the address in the Z-pointer are ignored. The BLBSET
bit will automatically be cleared upon completion of the Lock bit set, or if no SPM instruction is executed within four
clock cycles.
An (E)LPM instruction within three cycles after BLBSET and SPMEN are set in the SPMCSR Register, will read
either the Lock bits or the Fuse bits (depending on Z0 in the Z-pointer) into the destination register. See “Reading
the Fuse and Lock Bits from Software” on page 316 for details.
• Bit 2 – PGWRT: Page Write
If this bit is written to one at the same time as SPMEN, the next SPM instruction within four clock cycles executes
Page Write, with the data stored in the temporary buffer. The page address is taken from the high part of the Z-
pointer. The data in R1 and R0 are ignored. The PGWRT bit will auto-clear upon completion of a Page Write, or if
no SPM instruction is executed within four clock cycles. The CPU is halted during the entire Page Write operation if
the NRWW section is addressed.
Bit 76543210
0x37 (0x57)
SPMIE RWWSB SIGRD RWWSRE BLBSET PGWRT PGERS SPMEN SPMCSR
Read/Write R/W RR/W R/W R/W R/W R/W R/W
Initial Value00000000