mc68hc912bc32 Freescale Semiconductor, Inc, mc68hc912bc32 Datasheet - Page 179

• Manufacturer Part Number: mc68hc912bc32
• Description: M68hc12 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

The two 8-bit pulse accumulators, PAC1 and PAC0, are cascaded to form the PACB 16-bit pulse
accumulator. When PACB in enabled, (PBEN = 1 in PBCTL, $B0) the PACN1 and PACN0 register
contents are, respectively, the high and low bytes of the PACB.
When PACN1 overflows from $FF to $00, the interrupt flag PBOVF in PBFLG ($B1) is set. Full count
register access should take place in one clock cycle. A separate read/write for high byte and low byte will
give a different result than accessing them as a word.
13.4.14 16-Bit Modulus Down-Counter Control Register
Read: Anytime
Write: Anytime
MCZI — Modulus Counter Underflow Interrupt Enable Bit
MODMC — Modulus Mode Enable Bit
RDMCL — Read Modulus Down-Counter Load Bit
ICLAT — Input Capture Force Latch Action Bit
FLMC — Force Load Register into the Modulus Counter Count Register Bit
Freescale Semiconductor
When input capture latch mode is enabled (LATQ and BUFEN bit in ICSYS ($AB) are set), writing 1 to
this bit immediately forces the contents of the input capture registers TC0 to TC3 and their
corresponding 8-bit pulse accumulators to be latched into the associated holding registers. The pulse
accumulators will be automatically cleared when the latch action occurs.
Writing 0 to this bit has no effect. Read of this bit aways will return 0.
This bit is active only when the modulus down-counter is enabled (MCEN = 1). Writing a 1 into this bit
loads the load register into the modulus counter count register. This also resets the modulus counter
prescaler. Writing 0 to this bit has no effect.
When MODMC = 0, the counter starts counting and stops at $0000. Reads of this bit will return
always 0.
0 = Modulus counter interrupt is disabled.
1 = Modulus counter interrupt is enabled.
0 = The counter counts once from the value written to it and will stop at $0000.
1 = Modulus mode is enabled. When the counter reaches $0000, the counter is loaded with the
0 = Reads of the modulus count register will return the present value of the count register.
1 = Reads of the modulus count register will return the contents of the load register.
latest value written to the modulus count register.
Figure 13-35. 16-Bit Modulus Down-Counter Control Register (MCCTL)
Address: $00A6
For proper operation, the MCEN bit should be cleared before modifying the
MODMC bit to reset the modulus counter to $FF.
Reset:
Read:
Write:
MCZI
Bit 7
0
MODMC
6
0
M68HC12B Family Data Sheet, Rev. 9.1
RDMCL
5
0
NOTE
ICLAT
4
0
FLMC
3
0
MCEN
2
0
MCPR1
1
0
MCPR0
Bit 0
0
Timer Registers
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