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12.4.1 ISPI Data Register
The ISPI data register (SPDR) contains data to be exchanged with external devices.
Either writing or reading this register clears any set interrupt.
SPDR — ISPI Data Register
15
14
13
12
R
W
RESET:
0
0
0
Rx DATA — Receive Data
This read-only register contains the data bits received from the shift register. Those
bits more significant than the size determined in CLOCK COUNT (ISPI control regis-
ter) return zeros when read. For example, if CLOCK COUNT = 0x8 (9-bit transfer),
then bits 15 to 9 are forced to zeros. The value in this register is updated at the end of
every transfer.
Tx DATA — Transmit Data
This write-only register contains the data bits to be transmitted to the external device.
Data is copied from this register to the shift register at the time that the XCH bit is set.
As data is shifted MSB first, outgoing data is MSB-justified relative to the CLOCK
COUNT field in the ISPI control register. For example, if the exchange length is ten
bits (CLOCK COUNT = 0x9), the MSB of the outgoing data is bit nine. The first bit
presented to the external device is bit 9, followed by the remaining nine less signifi-
cant bits.
12.4.2 ISPI Control Register
The ISPI control register (SPCR), along with the ISPI interval control register, controls
the operation of the ISPI. Follow this sequence when changing operating modes:
1. Disable the ISPI (COUNT=0) without affecting other fields.
2. Wait for any transfer to complete (XCH bit clear).
3. Update to the new mode.
4. Re-enable the ISPI (COUNT = newcount).
SPCR — ISPI Control Register
15
14
13
12
R
DOZE SPI_EN SNS
DRV
W
RESET:
0
0
0
MMC2001
REFERENCE MANUAL
All manuals and user guides at all-guides.com
Freescale Semiconductor, Inc.
11
10
9
0
0
0
0
Figure 12-3 ISPI Data Register
11
10
9
MSTR IRQ_EN PHA
0
0
0
0
Figure 12-4 ISPI Control Register
INTERVAL MODE SERIAL PERIPHERAL INTERFACE
For More Information On This Product,
Go to: www.freescale.com
8
7
6
5
Rx DATA
Tx DATA
0
0
0
0
8
7
6
5
POL
SPIGP
BAUD RATE
0
0
0
0
10008000
4
3
2
1
0
0
0
0
10008002
4
3
2
1
CLOCK COUNT
0
0
0
0
MOTOROLA
0
0+
0
0
12-5
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