MPC8280 datasheet(1294/1386 Pages) FREESCALE

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Serial Peripheral Interface (SPI)

MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

39-10

Freescale Semiconductor

39.4.3

SPI Command Register (SPCOM)

The SPI command register (SPCOM), shown in Figure 39-8, is used to start SPI operation.

Table 39-4 describes the SPCOM fields.

39.5

SPI Parameter RAM

The SPI parameter RAM area is similar to the SCC general-purpose parameter RAM. The CP accesses the

SPI parameter table using a user-programmed pointer (SPI_BASE) located in the parameter RAM; see

Section 14.5.2, “Parameter RAM.” The SPI parameter table can be placed at any 64-byte aligned address

in the dual-port RAM’s general-purpose area (banks 1–8, 11 and 12). Some parameter values must be

user-initialized before the SPI is enabled; the CP initializes the others. Once initialized, parameter RAM

values do not usually need to be accessed. They should be changed only when the SPI is inactive.

Table 39-5 shows the memory map of the SPI parameter RAM.

BSY

Busy. Set after the first character is received but discarded because no Rx buffer is available.

TXB

Tx buffer. Set when the Tx data of the last character in the buffer is written to the Tx FIFO. Wait two

character times to be sure data is completely sent over the transmit signal.

RXB

Rx buffer. Set after the last character is written to the Rx buffer and the BD is closed.

Field

STR

—

Reset

0000_0000

R/W

Write Only

Addr

0x11AAD

Figure 39-8. SPCOM—SPI Command Register

Table 39-4. SPCOM Field Descriptions

Bits

Name

Description

STR

Start transmit. For an SPI master, setting STR causes the SPI to start transferring data to and from

the Tx/Rx buffers if they are prepared. For a slave, setting STR when the SPI is idle causes it to load

the Tx data register from the SPI Tx buffer and start sending with the next SPICLK after SPISEL is

asserted. STR is cleared automatically after one system clock cycle.

1–7

—

Reserved and should be cleared.

Table 39-3. SPIE/SPIM Field Descriptions (continued)

Bits

Name

Description

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