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UM10360_0
© NXP B.V. 2009. All rights reserved.
User manual
Rev. 00.06 — 5 June 2009
509 of 808
NXP Semiconductors
UM10360
Chapter 25: LPC17xx Motor Control PWM
7.10 MCPWM Capture Registers
7.10.1 MCPWM Capture read addresses (MCCAP0-2 - 0x400B 8044, 0x400B 8048,
0x400B 804C)
The MCCAPCON register (
) allows software to select any edge(s) on any of
the MCI0-2 inputs as a capture event for each channel. When a channel’s capture event
occurs, the current TC value for that channel is stored in its read-only Capture register.
These addresses are read-only, but the underlying registers can be cleared by writing to
the CAP_CLR address
7.10.2 MCPWM Capture clear address (MCCAP_CLR - 0x400B 8074)
Writing ones to this write-only address clears the selected CAP register(s).
8.
PWM operation
8.1 Pulse-width modulation
Each channel of the MCPWM has two outputs, A and B, that can drive a pair of transistors
to switch a controlled point between two power rails. Most of the time the two outputs have
opposite polarity, but a dead-time feature can be enabled (on a per-channel basis) to
delay both signals’ transitions from “passive” to “active” state so that the transistors are
never both turned on simultaneously. In a more general view, the states of each output
pair can be thought of “high”, “low”, and “floating” or “up”, “down”, and “center-off”.
Each channel’s mapping from “active” and “passive” to “high” and “low” is programmable.
After Reset, the three A outputs are passive/low, and the B outputs are active/high.
The MCPWM can perform edge-aligned and center-aligned pulse-width modulation.
4
CCPA2
0 = MCOA2 passive, 1 = MCOA2 tracks internal MCOA0.
0
5
CCPB2
0 = MCOB2 passive, 1 = MCOB2 tracks internal MCOA0.
0
31:6
-
Reserved.
Table 458. MCPWM Communication Pattern register (MCCP - address 0x400B 8040) bit
description
Bit
Symbol
Description
Reset
value
Table 459. MCPWM Capture read addresses (MCCAP0/1/2 - 0x400B 8044, 0x400B 8048,
0x400B 804C) bit description
Bit
Symbol
Description
Reset value
31:0
CAP0/1/2
TC value at a capture event for channel 0, 1, 2.
0x0000 0000
Table 460. MCPWM Capture clear address (CAP_CLR - 0x400B 8074) bit description
Bit
Symbol
Description
0
CAP_CLR0
Writing a 1 to this bit clears the MCCAP0 register.
1
CAP_CLR1
Writing a 1 to this bit clears the MCCAP1 register.
2
CAP_CLR2
Writing a 1 to this bit clears the MCCAP2 register.
31:3
-
Reserved