Z86229NBSP View Datasheet(PDF) - Zilog

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Z86229NBSP

CMOS Z8 8K ROM CONSUMER CONTROLLER PROCESSOR

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HSQR. These timing signals are used in the data output (dis-

play) circuits.

The H signal is further divided in the LINE and FLD CNTR

to produce the various decodes used to establish vertical

lock, time displays, and control functions required for prop-

er operation. The H signal is also used to generate the

Smooth Scroll timing signal for display.

The V Lock circuits produce a noise free vertical pulse de-

rived from the horizontal timing signal. When the user se-

lects Video as the vertical lock source, the internal synchro-

nizing signals are phased up with the incoming video by

comparing the internally generated vertical pulse to an input

vertical pulse. These pulses are derived from the Comp Sync

signal provided by the Sync Slicer. In the vertical lock set

to VIN mode, the VIN signal is used in place of the signal

derived from Comp Sync. In either case, when proper phas-

ing has been established, this circuit outputs the LOCK sig-

nal which is used to provide additional noise immunity to

the slicing circuits.

The LOCKed state is established only after several succes-

sive fields have occurred and the two vertical pulses remain

in sync. When LOCKed, the internal timing will flywheel

until the timing of the two vertical pulses lose coincidence

for a number of consecutive fields. Until LOCK is estab-

lished, the decoder operates on a pulse-by-pulse basis.

Command Processor

The Command Processor circuit controls the manipulation

of the data for storage and display. This circuit processes

the Control Port input commands to determine the display

status required and the data channel selected. During the dis-

play time (lines 43–237), this information is used to control

the loading, addressing, clearing of the Display RAM, and

the operations of the Character ROM and Output Logic cir-

cuits.

During data recovery time (TV lines 21–42), the Command

Processor, in conjunction with the data recovery circuits, re-

covers the XDS data and the data for the selected data chan-

nel. Data is sent to the RAM for storage and display and/or

to the serial port, as appropriate. Where necessary, the Com-

mand Processor converts the input data to the appropriate

form.

Output Logic

The Output Logic circuits operate together to generate the

output color signals RED, GREEN and BLUE, and the Box

signal. When MONOchrome mode is selected, all three col-

or outputs carry the luminance information. These outputs

are positive output logic signals.

The character ROM contains the dot pattern for all the char-

acters. The output logic provides the hardware underline,

graphics characters, and the Italics slant-generator circuits.

The smooth scroll display is achieved by the smooth scroll

counter logic, which controls the addressing of the Charac-

ter ROM.

Decoder Control Circuit

The Decoder Control Circuit block is the users communi-

cations port. The circuit converts the information provided

to the control port into the necessary internal control signals

required to establish the operating mode of the decoder. This

port can be operated in one of two serial modes. The SMS

pin is used to establish either of the two serial control modes.

In the two wire (I2C) control mode, the Z86229 responds

to its slave address for both the read and write conditions.

If the read bit is Low (indicating a WRITE sequence), then

the Z86229 responds with an acknowledge. The master

should then send an address byte followed by a data byte.

If the read bit is High (indicating a READ sequence), then

the Z86229 responds with an acknowledge followed by a

status byte and a data byte, respectively. Read data, how-

ever, is only available through indirect addressing; write ad-

dressing exhibits both indirect and direct modes. The busy

bit in the status byte indicates whether the write operation

has been completed or if read data is available.

The SPI mode is a three wire bus with the Z86229 acting

as the slave device. Communication is synchronized by the

SCK signal generated by the master. Typically, the serial

data output is transmitted on the falling edge of SCK and

the received data is captured on the rising edge of SCK. All

data is exchanged as 8-bit bytes.

Voltage/Current Reference

The Voltage/Current Reference circuit uses an externally-

connected resistor to establish the reference levels that are

used throughout the Z86229. For a minimal cost, an external

resistor can provide improved internal precision.



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