Rainbow Electronics AT89LP216 User Manual
Page 52
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3621A–MICRO–6/06
AT89LP216 [Preliminary]
Table 18-3.
SPSR – SPI Status Register
SPSR Address = E8H
Reset Value = 000X X000B
Not Bit Addressable
SPIF
WCOL
LDEN
–
–
SSIG
DISSO
ENH
Bit
7
6
5
4
3
2
1
0
Symbol Function
SPIF
SP interrupt flag. When a serial transfer is complete, the SPIF bit is set and an interrupt is generated if SPIE = 1 and
ES = 1. The SPIF bit is cleared by reading the SPI status register followed by reading/writing the SPI data register.
WCOL
When ENH = 0: Write collision flag. The WCOL bit is set if the SPI data register is written during a data transfer. During
data transfer, the result of reading the SPDR register may be incorrect, and writing to it has no effect. The WCOL bit
(and the SPIF bit) are cleared by reading the SPI status register followed by reading/writing the SPI data register.
When ENH = 1: WCOL works in Enhanced mode as Tx Buffer Full. Writing during WCOL = 1 in enhanced mode will
overwrite the waiting data already present in the Tx Buffer. In this mode, WCOL is no longer reset by the SPIF reset but
is reset when the write buffer has been unloaded into the serial shift register.
LDEN
Load enable for the Tx buffer in enhanced SPI mode.
When ENH is set, it is safe to load the Tx Buffer while LDEN = 1 and WCOL = 0. LDEN is high during bits 0 - 3 and is low
during bits 4 - 7 of the SPI serial byte transmission time frame.
SSIG
Slave Select Ignore. If SSIG = 0, the SPI will only operate in slave mode if SS (P1.4) is pulled low. When SSIG = 1, the
SPI ignores SS in slave mode and is active whenever SPE (SPCR.6) is set. P1.4 may be used as a regular I/O pin when
SSIG = 1.
DISSO
Disable slave output bit.
When set, this bit causes the MISO pin to be tri-stated so more than one slave device can share the same interface with
a single master. Normally, the first byte in a transmission could be the slave address and only the selected slave should
clear its DISSO bit.
ENH
Enhanced SPI mode select bit. When ENH = 0, SPI is in normal mode, i.e. without write double buffering.
When ENH = 1, SPI is in enhanced mode with write double buffering. The Tx buffer shares the same address with the
SPDR register.