AT90USB646 Datasheet, PDF (37/434 Pages) ATMEL Corporation – Microcontroller with 64/128K Bytes of ISP Flash and USB Controller

AT90USB64/128
Assembly Code Example⁽¹⁾
; OFFSET is defined to 0x4000 to ensure
; external memory access
; Configure Port C (address high byte) to
; output 0x00 when the pins are released
; for normal Port Pin operation
ldi r16, 0xFF
out DDRC, r16
ldi r16, 0x00
out PORTC, r16
; release PC7:6
ldi r16, (1<<XMM1)
sts XMCRB, r16
; write 0xAA to address 0x0001 of external
; memory
ldi r16, 0xaa
sts 0x0001+OFFSET, r16
; re-enable PC7:6 for external memory
ldi r16, (0<<XMM1)
sts XMCRB, r16
; store 0x55 to address (OFFSET + 1) of
; external memory
ldi r16, 0x55
sts 0x0001+OFFSET, r16
C Code Example⁽¹⁾
#define OFFSET 0x4000
void XRAM_example(void)
{
unsigned char *p = (unsigned char *) (OFFSET + 1);
DDRC = 0xFF;
PORTC = 0x00;
XMCRB = (1<<XMM1);
*p = 0xaa;
XMCRB = 0x00;
*p = 0x55;
}
Note: 1. See “About Code Examples” on page 8.
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