
Programmable Four-Channel Communications Controller
—
CD2481
Datasheet
199
9.7.3.2
General Timer 1 high (GT1h)
–
Sync Modes Only
9.7.4
General Timer 2 (GT2)
–
Sync Modes Only
This 16-bit timer can be started by the user whenever it is inactive by writing a 16-bit time-out
value to the register. When non-zero, it is decremented on each prescaler clock
‘
tick
’
. When it
reaches zero, a modem/timer group interrupt is generated to the host. The timer can be disabled by
the Channel Command register. In addition, during a receive or transmit interrupt, the user can
reload a running timer (high byte only) by providing a reload value in the Interrupt Status register
and a reload timer command in the End of Interrupt register for the interrupt being serviced. Only
one general timer can be restarted this way in a single-interrupt routine.
This 8-bit timer can be started by the user whenever it is inactive by writing an 8-bit time-out value
to the Timer register. When non-zero, it is decremented on each prescaler clock
‘
tick
’
. When it
reaches zero, a modem/timer group interrupt is generated to the host. The timer can be disabled by
the Channel Command register if the timer
’
s current value is greater than one. In addition, during a
receive or transmit interrupt, the user can reload a running timer by providing a reload value in the
Interrupt Status register and a reload timer command in the End of Interrupt register for the
interrupt being serviced. Only one general timer can be restarted this way in a single-interrupt
routine.
Register Name: GT1h
Register Description: General Timer 1, low byte
Default Value: x
’
00
Access: Byte Read/Write
Intel Hex Address: x
’
29
Motorola Hex Address: x
’
2A
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Binary Value, bits 15 - 8
Register Name: GT2
Register Description: General Timer 2
Default Value: x
’
00
Access: Byte Read/Write
Intel Hex Address: x
’
2A
Motorola Hex Address: x
’
29
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Binary Value