IBM MiEM78P468N IOCB0/CNT1PR Counter 1 Preset Register, IOCC0/CNT2PR Counter 2 Preset Register

EM78P468N/EM78P468L

8-Bit Microcontroller

6.2.8IOCB0/CNT1PR (Counter 1 Preset Register)

(Address: 0Bh, Bit 0 of R5 = “0”)

Bit 7	Bit 6	Bit 5	Bit 4	Bit 3	Bit 2	Bit 1	Bit 0
Bit 7	Bit 6	Bit 5	Bit 4	Bit 3	Bit 2	Bit 1	Bit 0

Bit 7 ~ Bit 0: These are Counter 1 buffers which user can read and write. Counter 1 is an 8-bit down-count timer with 8-bit prescaler used to preset the counter and read the preset value. The prescaler is set by the IOC91 register. After an interrupt, it will auto reload the preset value.

6.2.9IOCC0/CNT2PR (Counter 2 Preset Register)

(Address: 0Ch, Bit 0 of R5 = “0”)

Bit 7	Bit 6	Bit 5	Bit 4	Bit 3	Bit 2	Bit 1	Bit 0
Bit 7	Bit 6	Bit 5	Bit 4	Bit 3	Bit 2	Bit 1	Bit 0

Bit 7 ~ Bit 0: These are Counter 2 buffers which user can read and write. Counter 2 is an 8-bit down-count timer with 8-bit prescaler used to preset the counter and read the preset value. The prescaler is set by IOC91 register. After an interrupt, it will reload the preset value.

When IR output is enabled, this control register can obtain carrier frequency output. If the Counter 2 clock source is equal to FT , then

Carrier frequency (Fcarrier) =	FT
	2 * (preset _ value + 1) * prescaler

6.2.10 IOCD0/HPWTPR (High-Pulse Width Timer Preset Register)

(Address: 0Dh, Bit 0 of R5 = “0”)

Bit 7	Bit 6	Bit 5	Bit 4	Bit 3	Bit 2	Bit 1	Bit 0
Bit 7	Bit 6	Bit 5	Bit 4	Bit 3	Bit 2	Bit 1	Bit 0

Bit 7 ~ Bit 0: These are high-pulse width timer buffers which user can read and write. High-pulse width timer preset register is an eight-bit down-counter with 8-bit prescaler used as IOCD0 to preset the counter and read the preset value. The prescaler is set by the IOCA1 register. After an interrupt, it will reload the preset value.

For PWM or IR application, this control register is set as high pulse width.

If the high-pulse width timer clock source is FT , then

High pulse time = prescaler * (preset _ value + 1)

FT

Product Specification (V1.5) 02.15.2007 • 17

(This specification is subject to change without further notice)