C8051F124-GQR Datasheet, PDF (344/350 Pages) Silicon Laboratories – Mixed Signal ISP Flash MCU Family

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25.2. Flash Programming Commands
The Flash memory can be programmed directly over the JTAG interface using the Flash Control, Flash
Data, Flash Address, and Flash Scale registers. These Indirect Data Registers are accessed via the JTAG
Instruction Register. Read and write operations on indirect data registers are performed by first setting the
appropriate DR address in the IR register. Each read or write is then initiated by writing the appropriate
Indirect Operation Code (IndOpCode) to the selected data register. Incoming commands to this register
have the following format:
19:18
17:0
IndOpCode
WriteData
IndOpCode: These bit set the operation to perform according to the following table:
IndOpCode
0x
10
11
Operation
Poll
Read
Write
The Poll operation is used to check the Busy bit as described below. Although a Capture-DR is performed,
no Update-DR is allowed for the Poll operation. Since updates are disabled, polling can be accomplished
by shifting in/out a single bit.
The Read operation initiates a read from the register addressed by the DRAddress. Reads can be initiated
by shifting only 2 bits into the indirect register. After the read operation is initiated, polling of the Busy bit
must be performed to determine when the operation is complete.
The write operation initiates a write of WriteData to the register addressed by DRAddress. Registers of any
width up to 18 bits can be written. If the register to be written contains fewer than 18 bits, the data in Write-
Data should be left-justified, i.e. its MSB should occupy bit 17 above. This allows shorter registers to be
written in fewer JTAG clock cycles. For example, an 8-bit register could be written by shifting only 10 bits.
After a Write is initiated, the Busy bit should be polled to determine when the next operation can be initi-
ated. The contents of the Instruction Register should not be altered while either a read or write operation is
busy.
Outgoing data from the indirect Data Register has the following format:
19
18:1
0
0
ReadData
Busy
The Busy bit indicates that the current operation is not complete. It goes high when an operation is initiated
and returns low when complete. Read and Write commands are ignored while Busy is high. In fact, if poll-
ing for Busy to be low will be followed by another read or write operation, JTAG writes of the next operation
can be made while checking for Busy to be low. They will be ignored until Busy is read low, at which time
the new operation will initiate. This bit is placed ate bit 0 to allow polling by single-bit shifts. When waiting
for a Read to complete and Busy is 0, the following 18 bits can be shifted out to obtain the resulting data.
ReadData is always right-justified. This allows registers shorter than 18 bits to be read using a reduced
number of shifts. For example, the results from a byte-read requires 9 bit shifts (Busy + 8 bits).
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