MC9S12HZ256 Datasheet, PDF (276/692 Pages) Freescale Semiconductor, Inc – HCS12 Microcontrollers

Chapter 9 Motor Controller (MC10B8CV1)
9.4.1.3.2 Sign Bit (S)
Assuming RECIRC = 0 (the active state of the PWM signal is low), when the S bit for the corresponding
channel is cleared, MnC0P (if the PWM channel number is even, n = 0, 1, 2, 3, see Table 9-10) or MnC1P
(if the PWM channel number is odd, n = 0, 1, 2, 3, see Table 9-10), outputs a logic high while in (dual)
full H-bridge mode. In half H-bridge mode the state of the S bit has no effect. The PWM output signal is
generated on MnC0M (if the PWM channel number is even, n = 0, 1, 2, 3, see Table 9-10) or MnC1M (if
the PWM channel number is odd, n = 0, 1, 2, 3).
Assuming RECIRC = 0 (the active state of the PWM signal is low), when the S bit for the corresponding
channel is set, MnC0M (if the PWM channel number is even, n = 0, 1, 2, 3, see Table 9-10) or MnC1M
(if the PWM channel number is odd, n = 0, 1, 2, 3, see Table 9-10), outputs a logic high while in (dual)
full H-bridge mode. In half H-bridge mode the state of the S bit has no effect. The PWM output signal is
generated on MnC0P (if the PWM channel number is even, n = 0, 1, 2, 3, see Table 9-10) or MnC1P (if
the PWM channel number is odd, n = 0, 1, 2, 3).
Setting RECIRC = 1 will also invert the effect of the S bit such that while S = 0, MnC0P or MnC1P will
generate the PWM signal and MnC0M or MnC1M will be a static low output. While S = 1, MnC0M or
MnC1M will generate the PWM signal and MnC0P or MnC1P will be a static low output. In this case the
active state of the PWM signal will be high.
See Table 9-11 for detailed information about the impact of SIGN and RECIRC bit on the PWM output.
Table 9-11. Impact of RECIRC and SIGN Bit on the PWM Output
Output Mode
RECIRC
SIGN
MnCyM
MnCyP
(Dual) Full H-Bridge
0
0
PWM¹
1
(Dual) Full H-Bridge
(Dual) Full H-Bridge
0
1
1
0
1
PWM
0
PWM²
(Dual) Full H-Bridge
1
1
PWM
1
Half H-Bridge: PWM on MnCyM
Don’t care
Don’t care
PWM
—³
Half H-Bridge: PWM on MnCyP
Don’t care
Don’t care
—
PWM
1 _{PWM: The PWM signal is low active. e.g., the waveform starts with 0 in left aligned mode. Output M generates the PWM signal.}
Output P is static high.
2 _{PWM: The PWM signal is high active. e.g., the waveform starts with 1 in left aligned mode. output P generates the PWM signal.}
Output M is static low.
3 _{The state of the output transistors is not controlled by the motor controller.}
9.4.1.3.3 RECIRC Bit
The RECIRC bit controls the flow of the recirculation current of the load. Setting RECIRC = 0 will cause
recirculation current to flow through the high side transistors, and RECIRC = 1 will cause the recirculation
current to flow through the low side transistors. The RECIRC bit is only active in (dual) full H-bridge
modes.
Effectively, RECIRC = 0 will cause a static high output on the output terminal not driven by the PWM,
RECIRC = 1 will cause a static low output on the output terminals not driven by the PWM. To achieve the
same current direction, the S bit behavior is inverted if RECIRC = 1. Figure 9-12, Figure 9-13,
Figure 9-14, and Figure 9-15 illustrate the effect of the RECIRC bit in (dual) full H-bridge modes.
MC9S12HZ256 Data Sheet, Rev. 2.04
276
Freescale Semiconductor