Altera Embedded Peripherals IP Instrukcja Użytkownika Strona 115

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Register Map
An Avalon-MM master peripheral controls and communicates with the SPI core via the six 32-bit
registers, shown in below in the Register Map for SPI Master Device figure. The table assumes an n-bit
data width for rxdata and txdata.
Table 10-5: Register Map for SPI Master Device
Interna
l
Addres
s
Register Name Type
[R/W]
32..11 10 9 8 7 6 5 4 3 2 1 0
0 rxdata (1) R RXDATA (n-1..0)
1 txdata (1) W TXDATA (n-1..0)
2 status (2) R/W E RRDY TRDY TMT TOE ROE
3 control R/W SSO
(3)
IE IRRDY ITRDY ITOE IROE
4 Reserved
5 slaveselect (3) R/W Slave Select Mask
Table 10-5:
1. Bits 31 to n are undefined when n is less than 32.
2. A write operation to the status register clears the ROE, TOE, and E bits.
3. Present only in master mode.
Reading undefined bits returns an undefined value. Writing to undefined bits has no effect.
rxdata Register
A master peripheral reads received data from the rxdata register. When the receive shift register receives
a full n bits of data, the status register's RRDY bit is set to 1 and the data is transferred into the rxdata
register. Reading the rxdata register clears the RRDY bit. Writing to the rxdata register has no effect.
New data is always transferred into the rxdata register, whether or not the previous data was retrieved. If
RRDY is 1 when data is transferred into the rxdata register (that is, the previous data was not retrieved), a
receive-overrun error occurs and the status register's ROE bit is set to 1. In this case, the contents of
rxdata are undefined.
txdata Register
A master peripheral writes data to be transmitted into the txdata register. When the status register's
TRDY bit is 1, it indicates that the txdata register is ready for new data. The TRDY bit is set to 0 whenever
the txdata register is written. The TRDY bit is set to 1 after data is transferred from the txdata register
into the transmitter shift register, which readies the txdata holding register to receive new data.
A master peripheral should not write to the txdata register until the transmitter is ready for new data. If
TRDY is 0 and a master peripheral writes new data to the txdata register, a transmit-overrun error occurs
and the status register's TOE bit is set to 1. In this case, the new data is ignored, and the content of txdata
remains unchanged.
UG-01085
2014.24.07
Register Map
10-9
SPI Core
Altera Corporation
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