UM10208_2
© NXP B.V. 2007. All rights reserved.
User manual
Rev. 02 — 1 June 2007
296 of 362
NXP Semiconductors
UM10208
Chapter 23: LPC2800 SD/MMC
5.2 Power Control Register (MCIPower - 0x8010 0000)
The MCIPower register controls an external power supply. Power can be switched on and
off, and adjust the output voltage.
shows the MCIPower register.
When the external power supply is switched on, the software first enters the power-up
phase, and waits until the supply output is stable before moving to the power-on phase.
During the power-up phase, the pin used for the MCIPWR output should be set HIGH by
software. The card bus outlets are disabled during both phases.
Note: After a data write, data cannot be written to this register for three MCLK clock
periods plus two PCLK clock periods.
5.3 Clock Control Register (MCIClock - 0x8010 0004)
The MCIClock register controls the MCICLK output.
shows the clock control
register.
While the MCI is in identification mode, the MCICLK frequency must be less than
400 kHz. The clock frequency can be changed to the maximum card bus frequency when
relative card addresses are assigned to all cards.
Table 332. Power Control register (MCIPower - 0x8010 0000)
Bit
Symbol
Description
Reset
Value
1:0
Ctrl
00: Power-off
01: Reserved
10: Power-up
11: Power-on
00
5:2
-
Reserved, user software should not write ones to reserved bits.
The value read from a reserved bit is not defined.
-
6
OpenDrain MCICMD output control.
0
31:7
-
Reserved, user software should not write ones to reserved bits.
The value read from a reserved bit is not defined.
-
Table 333. Clock Control register (MCIClock - 0x8010 0004)
Bit
Symbol
Description
Reset
Value
7:0
ClkDiv
MCI bus clock period:
MCICLK frequency = MCLK / 2x(1).
0
8
ClkEnab
Write a 1 to this bit to enable the MCI bus clock
0
9
PwrSave
When this bit is 0, as it is after reset, the MCI bus clock runs
whenever the Enable bit above is 1. Write a 1 to this bit to stop the
clock when the bus is idle.
0
10
Bypass
When this bit is 0, as it is after reset, MCLK is divided by 1 to
produce MCICLK. Write a 1 to this bit to bypass this division and
drive MCICLK directly from MCLK.
0
11
WideBus
When this bit is 0, as it is after reset, only the MD0 line is used. Use
this mode for MCI cards. Write a 1 to this bit to use MD3:0 for
communicating with SD cards.
0
31:12
-
Reserved, user software should not write ones to reserved bits. The
value read from a reserved bit is not defined.
-