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AD1200 Reference
The AD1210-21 cards, with the 8254 counter timer chip on
board, uses the TIMER register bits 7 as a method of selecting
the 8254 counter timer INSTEAD on the on board 600kHz pacer
clock as the source of the A/D converter strobe pulses. Bit 6 has
no function and reads back as 0.
Figure 3-19. AD1200 Extended Mode Bits.
____________________________________ _
AD1200 Card Only TIMER Extended Mode Bits
BIT 7
BIT 6
0
0
0
1
1
0
1
1
______________________________________
Figure 3-20. AD1210-21 Extended Mode Bit.
AD1210-AD1221 TIMER Extended Mode Bits
BIT 7
BIT 6
0
Always= 0
1
Always= 0
The 8254 Counter Timer Registers.
______________________________ _
The AD1210-21 cards have an 8254 counter timer chip on
board, the base address of the 8254 is 8 byte before 8 registers
of the AD card. Thus for an AD1210 card with a base address
of 0218hex the 8254 counter timer is at 0210hex. The counter
timer occupies only four location, 0210-0213 hex, a shadow or
copy of these registers appears at 0214-0217 hex also. This
shadow copy of the registers does NOT mean that two counter
timers are present on the card.
Page 70
Continuous Conversion Performed On
A/D Converter
DAC0
DAC1
DIGITAL I/O PORT
A/D Clock Source
600kHz On Board Pacer Clock
8254 Timer Counter
Register Map
Compatible Mode
__________ _
Read/ Write
Chapter 3
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