ATmega64A datasheet(293/392 Pages) ATMEL

293 / 392 page

293

8160C–AVR–07/09

ATmega64A

Note:

1. Z0: should be zero for all SPM commands, byte select for the LPM instruction.

2. See “Addressing the Flash During Self-programming” on page 286 for details about the use of

Z-pointer during Self-programming.

26.9

26.9.1

SPMCSR – Store Program Memory Control Register

The Store Program Memory Control 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 initi-

ated, 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 – Res: Reserved Bit

This bit is a reserved bit in the ATmega64A and always read as zero.

Table 26-8.

Explanation of Different Variables Used in Figure 26-3 and the Mapping to the Z-

pointer(1)(2)

Variable

Corresponding

Z-value

Description

PCMSB

Most significant bit in the Program Counter. (The

Program Counter is 15 bits PC[14:0]).

PAGEMSB

Most significant bit which is used to address the

words within one page (128 words in a page

requires seven bits PC [6:0]).

ZPCMSB

Z15

Bit in Z-register that is mapped to PCMSB. Because

Z0 is not used, the ZPCMSB equals PCMSB + 1.

ZPAGEMSB

Bit in Z-register that is mapped to PAGEMSB.

Because Z0 is not used, the ZPAGEMSB equals

PAGEMSB + 1.

PCPAGE

PC[14:7]

Z15:Z8

Program Counter page address: Page select, for

Page Erase and Page Write

PCWORD

PC[6:0]

Z7:Z1

Program Counter word address: Word select, for

filling temporary buffer (must be zero during Page

Write operation)

Bit

765

(0x68)

SPMIE

RWWSB

–

RWWSRE

BLBSET

PGWRT

PGERS

SPMEN

SPMCSR

Read/Write

R/W

Initial Value

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