NEC PD17062 Manuale Utente

µ

The gate control register is a 2-bit register consisting of the HSCGT1 and HSCGT0 flags used to control the

gate.  It is mapped in the register file at 11H.  The gate control register can be read- and write-accessed through

the window register (system register) using the PEEK and POKE instructions, respectively.

The following modes can be set up using the gate control register.

Note The gate clock generator works only when this mode is selected.

In the gate closed mode, the gate is kept closed, disabling the HSC and gate clock generator from operating

(the content of the HSYNC counter does not change).  This mode also turns off the bias input to the horizontal

sync signal counter, and therefore it should be selected when the port is used.

This mode is selected at a power-on reset and a clock stop.

When the gate open mode is entered, the gate opens and causes the HSYNC counter to start counting the

input signal after it is reset.

When the HSYNC counter overflows, it goes back to 0.

In this mode, the input pin is biased.

When the 1.69 ms gate mode is entered, the HSYNC counter is reset and starts counting the input signal

after 3.375/2 ms (with an error of 0 to 62.5 

µ

s).  The gate is kept open for 1.69 ms.  The input pin is biased.

If the input signal is high when the gate is opened or closed, it is counted as one.

b

3

b

2

b

1

b

0

(RF11H)

HSCGT0

HSCGT1

HSCGT2

HSCGT3

0

0

1

0

1

0

1

1

Gate closed

Gate open

Open-gate time of 1.69 ms 

Not to be set

Fixed at 0