Rainbow Electronics ATtiny2313 - Manual (Page 157)

157
ATtiny2313
2543A–AVR–08/03
Store Program Memory
Control and Status Register –
SPMCSR The Store Program Memory Control and Status Register contains the control bits
needed to control the Program memory operations.
• Bits 7..5 – Res: Reserved Bits
These bits are reserved bits in the ATtiny2313 and always read as zero.
• Bit 4 – CTPB: Clear Temporary Page Buffer
If the CTPB bit is written while filling the temporary page buffer, the temporary page
buffer will be cleared and the data will be lost.
• Bit 3 – RFLB: Read Fuse and Lock Bits
An LPM instruction within three cycles after RFLB 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 “EEPROM Write Prevents Writing to
SPMCSR” on page 158 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.
• Bit 1 – PGERS: Page Erase
If this bit is written to one at the same time as SPMEN, the next SPM instruction within
four clock cycles executes Page Erase. The page address is taken from the high part of
the Z-pointer. The data in R1 and R0 are ignored. The PGERS bit will auto-clear upon
completion of a Page Erase, or if no SPM instruction is executed within four clock
cycles. The CPU is halted during the entire Page Write operation.
• Bit 0 – SPMEN: Store Program Memory Enable
This bit enables the SPM instruction for the next four clock cycles. If written to one
together with either CTPB, RFLB, PGWRT, or PGERS, the following SPM instruction
will have a special meaning, see description above. If only SPMEN is written, the follow-
ing SPM instruction will store the value in R1:R0 in the temporary page buffer addressed
by the Z-pointer. The LSB of the Z-pointer is ignored. The SPMEN bit will auto-clear
upon completion of an SPM instruction, or if no SPM instruction is executed within four
clock cycles. During Page Erase and Page Write, the SPMEN bit remains high until the
operation is completed.
Writing any other combination than “10001”, “01001”, “00101”, “00011” or “00001” in the
lower five bits will have no effect.
Bit 7 6 5 4 3 2 1 0
– – – CTPB RFLB PGWRT PGERS SPMEN SPMCSR
Read/Write R R R R/W R/W R/W R/W R/W
Initial Value 0 0 0 0 0 0 0 0