AT90S8515

Manufacturer Part NumberAT90S8515
Description8-bit microcontroller with 8K bytes in-system programmable flash, 2.7-6.0V
ManufacturerATMEL Corporation
AT90S8515 datasheet
 
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Page 50/112:

Bit DORD: Data Order

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SPI Status Register – SPSR
AT90S8515
50
• Bit 5 – DORD: Data Order
When the DORD bit is set (one), the LSB of the data word is transmitted first.
When the DORD bit is cleared (zero), the MSB of the data word is transmitted first.
• Bit 4 – MSTR: Master/Slave Select
This bit selects Master SPI Mode when set (one), and Slave SPI Mode when cleared
(zero). If SS is configured as an input and is driven low while MSTR is set, MSTR will be
cleared and SPIF in SPSR will become set. The user will then have to set MSTR to re-
enable SPI Master Mode.
• Bit 3 – CPOL: Clock Polarity
When this bit is set (one), SCK is high when idle. When CPOL is cleared (zero), SCK is
low when idle. Refer to Figure 36 and Figure 37 for additional information.
• Bit 2 – CPHA: Clock Phase
Refer to Figure 36 or Figure 37 for the functionality of this bit.
• Bits 1, 0 – SPR1, SPR0: SPI Clock Rate Select 1 and 0
These two bits control the SCK rate of the device configured as a master. SPR1 and
SPR0 have no effect on the slave. The relationship between SCK and the oscillator
clock frequency f
is shown in Table 16.
cl
Table 16. Relationship between SCK and the Oscillator Frequency
SPR1
SPR0
0
0
0
1
1
0
1
1
Bit
7
6
5
$0E ($2E)
SPIF
WCOL
Read/Write
R
R
R
Initial Value
0
0
0
• Bit 7 – SPIF: SPI Interrupt Flag
When a serial transfer is complete, the SPIF bit is set (one) and an interrupt is gener-
ated if SPIE in SPCR is set (one) and global interrupts are enabled. If SS is an input and
is driven low when the SPI is in Master Mode, this will also set the SPIF flag. SPIF is
cleared by hardware when executing the corresponding interrupt handling vector. Alter-
natively, the SPIF bit is cleared by first reading the SPI Status Register when SPIF is set
(one), then by accessing the SPI Data Register (SPDR).
• Bit 6 – WCOL: Write Collision Flag
The WCOL bit is set if the SPI Data Register (SPDR) is written during a data transfer.
The WCOL bit (and the SPIF bit) are cleared (zero) by first reading the SPI Status Reg-
ister when WCOL is set (one), and then by accessing the SPI Data Register.
• Bits 5..0 – Res: Reserved Bits
These bits are reserved bits in the AT90S8515 and will always read as zero.
The SPI interface on the AT90S8515 is also used for program memory and EEPROM
downloading or uploading. See page 86 for serial programming and verification.
SCK Frequency
/
f
4
cl
/
f
16
cl
/
f
64
cl
/
f
128
cl
4
3
2
1
0
R
R
R
R
R
0
0
0
0
0
SPSR
0841G–09/01