
MMC2001
PROGRAMMING REFERENCE
MOTOROLA
REFERENCE MANUAL
C-31
C.8.2 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).
2. Wait for any transfer to complete (XCH bit clear).
3. Update to the new mode.
4. Re-enable the ISPI (COUNT = newcount).
Figure C-33 ISPI Control Register
DOZE — Doze Mode
When the CPU executes a doze instruction and the system is placed in doze mode,
the DOZE bit affects operation of the ISPI. When this bit is set, the ISPI is disabled in
doze mode.
0 =
ISPI unaffected in doze mode
1 =
ISPI disabled in doze mode
At reset, this bit is cleared to zero.
SPI_EN — ISPI Enable
In either master mode, this bit controls the value of the SPI_EN pin. The sense of the
SPI_EN pin is determined by the SNS bit. In interval mode, the SPI_EN pin is
asserted only when XCH is active. The SPI_EN bit must be programmed to a one for
any master mode transfer to occur. In slave mode, the ISPI state machine uses the
input value on the SPI_EN pin, and this register bit is ignored. Further, the SPI_EN
register bit will not reflect the value of the SPI_EN pin in slave mode.
0 =
Negated
1 =
Asserted
SNS — SPI_EN Sense
The SNS bit controls the sense of the SPI_EN pin relative to the SPI_EN register bit
in the ISPI control register. This is required because in interval mode, the state
machine must assert and then negate the SPI_EN pin. The SNS bit has an affect only
when the SPI_EN pin is an output. If the SPI_EN pin is an input, then it is active low,
and the SNS bit has no effect.
0 =
SPI_EN pin is active low
1 =
SPI_EN pin is active high
SPCR — ISPI Control Register
10008002
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
R
DOZE
SPI_
EN
SNS
DRV
MSTR
IRQ_
EN
PHA
POL
SPIGP
BAUD RATE
CLOCK COUNT
W
RESET:
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
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I
Freescale Semiconductor, Inc.
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