TIA 1A - TELEVISION INTERFACE ADAPTOR (MODEL 1A)
1. Data and addressing
Registers on this chip are addressed by the microprocessor
as part of its overall RAM-ROM memory space. The attached
table of read-write addresses summarizes the addressable
functions. There are no registers that are both read and
write. Some addresses however are both read and write,
with write data going into one register and read data
returning from a different register.
If the read-write line is low, the data bits indicated in
this table will be written into the addressed write
location when the 02 clock goes from high to low. Some
registers are eight bits wide, some only one bit, and some
(strobes) have no bits, performing only control functions
(such as resets) when their address is written.
If the read-write line is high, the addressed location can
be read by the microprocessor on data lines 6 and 7 while
the 02 clock is high.
The addresses given in the table refer only to the six (6)
real address lines. If any of the four (4) chip select
lines are used for addressing, the addresses must be