CD2231 Intel Corporation, CD2231 Datasheet - Page 155

• Manufacturer Part Number: CD2231
• Description: CD2231 Intelligent Two-channel Lan And Wan Communications Controller
• Manufacturer: Intel Corporation

8.7.5
Datasheet
Register Name: TTR
Register Description: Transmit Timer
Default Value: x’00
Access: Byte Read only
Bit 7
This 16-bit timer can be started by the user whenever it is inactive by writing a 16-bit timeout 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 timeout 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.
Transmit Timer Register (TTR) Async Modes Only
This Asynchronous mode timer is managed by the CD2231 to implement embedded transmit
delays when that option is used by the host (see description of Channel Option Register 2). This
register should not be modified by the host under any circumstances.
Bit 6
Intelligent Two-Channel LAN and WAN Communications Controller — CD2231
Bit 5
Bit 4
Binary value
Bit 3
Bit 2
Motorola Hex Address: x’29
Bit 1
Intel Hex Address: x’2A
Bit 0
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