ly, in
register $213C, but only after $2137 has been read once.&nbsp; For the
vertical counter, the low byte of the scanline is sent, followed by the
high byte, and afterwards nothing but zeros (until $2137 is read again.)&nbsp;
One doc suggests register $213F is related to this register, but I don't
know how so.

<P><A NAME="Reg4200"></A><B><FONT FACE="Lucida Console">Register $4200:
Counter Enable (1b/W)</FONT></B>
<PRE>n-vh---j&nbsp; n: NMI Interrupt enable&nbsp; v: vertical counter enable
&nbsp;&nbsp;&n