General Circuit Interface (GCI)
Am186™CC/CH/CU Microcontrollers User’s Manual
17-11
reception as soon as DCL appears; no intervention from the controller is required. However,
the microcontroller must respond to the interrupt and perform the normal C/I channel
software handshakes before activation completes.
17.5.4.2
GCI Bus Reversal
In Terminal mode, a device may be required to transmit both upstream and downstream,
based on which GCI channel is being transmitted at any one time. As a result, the actual
data pins of the GCI interface need to be both inputs and outputs, changing direction based
on which channel is being transmitted at the time.
17.5.4.2.1
Downstream Versus Upstream
The following terms are used in GCI:
Downstream Direction: Data is output on GCI_DD_A by an upstream device and this data
is a GCI_DU_A input to the downstream device.
Upstream Direction: Data is output on GCI_DU_A by a downstream device and this data
is a GCI_DD_A input to the upstream device.
Downstream Device: Generates GCI_DU_A and terminates GCI_DD_A.
Upstream Device: Generates GCI_DD_A and terminates GCI_DU_A.
Because pin reversal is supported, a device on the GCI bus can be considered a
downstream device, an upstream device, or both. Figure 17-5 demonstrates the Am186CC
microcontroller as an GCI Subframe 0 downstream device (the transceiver, an upstream
device, outputs data on GCI_DD_A and the Am186CC microcontroller, the downstream
device, inputs data from GCI_DD_A).
Figure 17-5 also demonstrates the Am186CC microcontroller as a GCI Subframe 1
upstream device (the Am186CC microcontroller, an upstream device, outputs data on
GCI_DD_A and a downstream device, such as an GCI codec, inputs data from GCI_DD_A).
Devices which do not support pin reversal are fixed to transmit and receive in one direction
only.
For example, a line transceiver is always an upstream device communicating solely with
downstream devices (it transmits information on GCI_DD_A to downstream devices, and
receives information on GCI_DU_A from devices sending information upstream to this
upstream transceiver). Therefore, in this case, anything on the GCI bus is always considered
downstream from the upstream transceiver.
Note: In most documentation, where a reference point is not given, but upstream or
downstream are mentioned, the default reference point is almost always the transceiver:
that is, downstream (from the transceiver), upstream (to the transceiver), the upstream
(transceiver) device, and so on.
Содержание Am186 CC
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Страница 18: ...Table of Contents xviii Am186 CC CH CU Microcontrollers User s Manual...
Страница 24: ...Introduction xxiv Am186 CC CH CU Microcontrollers User s Manual...
Страница 39: ...Architectural Overview Am186 CC CH CU Microcontrollers User s Manual 1 15 Figure 1 6 32 Channel Linecard CH CC...
Страница 40: ...Architectural Overview 1 16 Am186 CC CH CU Microcontrollers User s Manual...
Страница 86: ...System Overview 3 36 Am186 CC CH CU Microcontrollers User s Manual...
Страница 92: ...Emulator Support 4 6 Am186 CC CH CU Microcontrollers User s Manual...
Страница 112: ...DRAM Controller 6 8 Am186 CC CH CU Microcontrollers User s Manual...
Страница 134: ...Interrupts 7 22 Am186 CC CH CU Microcontrollers User s Manual...
Страница 186: ...Programmable I O Signals 9 8 Am186 CC CH CU Microcontrollers User s Manual...
Страница 200: ...Watchdog Timer 11 6 Am186 CC CH CU Microcontrollers User s Manual...
Страница 232: ...Asynchronous Serial Ports UARTs 13 24 Am186 CC CH CU Microcontrollers User s Manual...
Страница 242: ...Synchronous Serial Port SSI 14 10 Am186 CC CH CU Microcontrollers User s Manual...
Страница 264: ...High Level Data Link Control HDLC 15 22 Am186 CC CH CU Microcontrollers User s Manual...
Страница 332: ...Universal Serial Bus USB 18 34 Am186 CC CH CU Microcontrollers User s Manual...
Страница 348: ...Register Summary A 16 Am186 CC CH CU Microcontrollers User s Manual...
Страница 376: ...Index Index 18 Am186 CC CH CU Microcontrollers User s Manual...