Chapter 12 Pulse-Width Modulator (S12PWM8B8CV1)
MC9S12XDP512 Data Sheet, Rev. 2.11
570 Freescale Semiconductor
Read: Anytime
Write: Anytime
NOTE
PCKB2–0 and PCKA2–0 register bits can be written anytime. If the clockpre-scale is changed while a PWM signal is being generated, a truncated orstretched pulse can occur during the transition.
s
Module Base + 0x0003
76543210
R0 PCKB2 PCKB1 PCKB0 0PCKA2 PCKA1 PCKA0
W
Reset 00000000
= Unimplemented or Reserved

Figure 12-6. PWM Prescale Clock Select Register (PWMPRCLK)

Table 12-4. PWMPRCLK Field Descriptions

Field Description
6–4
PCKB[2:0]
Prescaler Select for Clock B — Clock B is one of two clock sources which can be used for channels 2, 3, 6, or
7. These three bits determine the rate of clock B, as shown in Table 12-5.
2–0
PCKA[2:0]
Prescaler Select for Clock A — Clock A is one of two clock sources which can be used for channels 0, 1, 4 or
5. These three bits determine the rate of clock A, as shown in Table 12-6.

Table 12-5. Clock B Prescaler Selects

PCKB2 PCKB1 PCKB0 Value of Clock B
0 0 0 Bus clock
0 0 1 Bus clock / 2
0 1 0 Bus clock / 4
0 1 1 Bus clock / 8
1 0 0 Bus clock / 16
1 0 1 Bus clock / 32
1 1 0 Bus clock / 64
1 1 1 Bus clock / 128

Table 12-6. Clock A Prescaler Selects

PCKA2 PCKA1 PCKA0 Value of Clock A
0 0 0 Bus clock
0 0 1 Bus clock / 2
0 1 0 Bus clock / 4
0 1 1 Bus clock / 8
1 0 0 Bus clock / 16
1 0 1 Bus clock / 32
1 1 0 Bus clock / 64
1 1 1 Bus clock / 128