COBHAM GR712RC User Manual

GR712RC-UM, Jun 2017, Version 2.9 222 www.cobham.com/gaisler
GR712RC
28 Clock Gating Unit
28.1 Overview
The CLKGATE clock gating unit provides a mean to save power by disabling the clock to unused
functional blocks.
28.2 Operation
The operation of the clock gating unit is controlled through three registers: the unlock, clock enable
and core reset registers. The clock enable register defines if a clock is enabled or disabled. A ‘1’ in a
bit location will enable the corresponding clock, while a ‘0’ will disable the clock. The core reset reg-
ister allows to generate a reset signal for each generated clock. A reset will be generated as long as the
corresponding bit is set to ‘1’. The bits in clock enable and core reset registers can only be written
when the corresponding bit in the unlock register is 1. If a bit in the unlock register is 0, the corre-
sponding bits in the clock enable and core reset registers cannot be written.
To gate the clock for a core, the following procedure should be applied:
1. Disable the core through software to make sure it does not initialize any AHB accesses
2. Write a 1 to the corresponding bit in the unlock register
3. Write a 1 to the corresponding bit in the core reset register
4. Write a 0 to the corresponding bit in the clock enable register
5. Write a 0 to the corresponding bit in the unlock register
To enable the clock for a core, the following procedure should be applied
1. Write a 1 to the corresponding bit in the unlock register
2. Write a 1 to the corresponding bit in the core reset register
3. Write a 1 to the corresponding bit in the clock enable register
4. Write a 0 to the corresponding bit in the core reset register
5. Write a 0 to the corresponding bit in the unlock register
The cores connected to the clock gating unit are defined in the table below:
Table 242.Clocks controlled by CLKGATE unit in the GR712RC
Bit Functional module
0 GRETH 10/100 Mbit Ethernet MAC
1 GRSPW SpaceWire link 0
2 GRSPW SpaceWire link 1
3 GRSPW SpaceWire link 2
4 GRSPW SpaceWire link 3
5 GRSPW SpaceWire link 4
6 GRSPW SpaceWire link 5
7 CAN core 0 & 1
8 Proprietary, never enable this function
9 CCSDS Telemetry encoder
10 CCSDS Telecommand decoder
11 MIL-STD-1553 BC/RT/MT

COBHAM GR712RC Specifications

General

Brand	COBHAM
Model	GR712RC
Category	Computer Hardware
Language	English