Functional Description

Index SRAM

The 256 X 4 bits index SRAM is used for applications that need more SRAM or need to load addresses by

operation, and data SRAM is included at a lower-half address in the index SRAM.

Index ROM

The 256 X 8 bits index ROM can be used in the 4-bit or 8-bit mode.

I/O ports

The IOA port can be selected by software separately as input or output. It can also be selected with/without

internal pull-low and different chattering clocks for a HALT release / interrupt trigger in order to reduce the

input bounce for the key scan:

PH6: 512Hz, PH8: 128Hz, PH10: 32Hz.

The pull-low of IOA will be masked off for those pins defined as output pins:

The IOA port can be used as a pseudo serial output port.

The IOB port can be selected by software separately as input or output.

Th e IOC port can be selected by software separately as input or output, and with/without internal pull-low and

different chattering clocks for a HALT release /interrupt trigger in order to reduce the bounce of the key scan.

The pull-low of the IOC will be masked off for those pins defined as output pins.

The IOD port can be selected by software separately as input or output.

The IOD port can be used as a pseudo serial output port.

The initial state of all I/O ports is the standard input state, and IOA and C have pull-low.

Before setting the I/O ports from input to output, execute the output function first to ensure the output state.

Resistor to frequency converter

We use an RC oscillation circuit and a 16-bit counter to calculate the relative resistance of temperature and

humidity sensor. The diagram is shown below:

RT

RH

RR

CX

ELP

RHM

Rref

CX

ENX

EHM

FIN

ERR

ENX

FIN

Freq.

CL

LD

16-Bit Counter

4-Bit Data Bus

Freq.

CL

LD

TMS

PH9

MRF

Timer & R/F

Controller

RTP

There are 2 methods for measuring the input frequency. First, set FIN (i.e. CX) as the clock input and use

timer 2 or the software directly as interval control. Second, if the FIN (CX) frequency is too low (either because

of a poor resolution for a fixed interval or a longer interval for better resolution but a longer read-out rate,

ex.10 seconds per read-out), you can switch the measure mode to set FIN (CX) as the interval control. It will

Preliminary

9

Ver. 0.0

APU428