|
Test Mode
TEST provides a pass through for reading the state of the DIR and CLK
pins and counter Reset
TEST |
Result |
0 |
- Normal counting based on DIR & CLK
- A read operation puts counter selected by A0, A1 onto the DQ
outputs
|
1 |
- All counters are rest
- The inverted state of the DIR and CLK inputs are passed
through to the DQ outputs during a read
- A0/A1 inputs are meaningless, all addresses of the chip return
the same result.
|
On the Rampart board this is used to the read the state of the
joystick inputs, for the 2 player version, quite a useful feature.
|
|
Corresponding DQ output to DIR & CLK pins with
TEST='1'
| DQ0 = inverted DIR0 |
| DQ1 = inverted CLK0 |
| DQ2 = inverted DIR1 |
| DQ3 = inverted CLK1 |
| DQ4 = inverted DIR2 |
| DQ5 = inverted CLK2 |
| DQ6 = inverted DIR3 |
| DQ7 = inverted CLK3 | |