Parallel Gpio Bootloader Handshake Protocol; Parallel Gpio Boot 8-Bit Data Stream - Texas Instruments Concerto F28M35 Series Technical Reference Manual

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Bytes GPIO[ 9,8,5:0]
(Byte 1 of 2)
1 2 08
3 4 00
... ... ...
17 18 00
19 20 00
21 22 CC
23 24 MM
25 26 AA
27 28 CC
29 30 AA
...
...
. AA
. MM
. AA
. CC
. AA
.
n n+1 AA
n+2 n+3 00
The device first signals the host that it is ready to begin data transfer by pulling the GPIO26 pin low. The
host load then initiates the data transfer by pulling the GPIO27 pin low. The complete protocol is shown in
the diagram below:
1. The device indicates it is ready to start receiving data by pulling the GPI2O6 pin low.
2. The bootloader waits until the host puts data on GPIO [9,8,5:0]. The host signals to the device that
data is ready by pulling the GPIO27 pin low.
3. The device reads the data and signals the host that the read is complete by pulling GPIO26 high.
4. The bootloader waits until the host acknowledges the device by pulling GPIO27 high.
5. The device again indicates it is ready for more data by pulling the GPIO26 pin low.
This process is repeated for each data value to be sent.
Figure 6-7 shows an overview of the Parallel GPIO bootloader flow.
SPRUH22I – April 2012 – Revised November 2019
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Table 6-13. Parallel GPIO Boot 8-Bit Data Stream
GPIO[ 9,8,5:0] Description
(Byte 2 of 2)
AA 0x08AA (KeyValue for memory width = 16bits)
00 8 reserved words (words 2 - 9)
... ...
00 Last reserved word
BB Entry point PC[22:16]
DD Entry point PC[15:0] (PC = 0x00BBCCDD)
NN Block size of the first block of data to load = 0xMMNN words
BB Destination address of first block Addr[31:16]
DD Destination address of first block Addr[15:0] (Addr = 0xAABBCCDD)
BB First word of the first block in the source being loaded = 0xAABB
...
Data for this section.
...
BB Last word of the first block of the source being loaded = 0xAABB
NN Block size of the 2nd block to load = 0xMMNN words
BB Destination address of second block Addr[31:16]
DD Destination address of second block Addr[15:0]
BB First word of the second block in the source being loaded
...
BB Last word of the last block of the source being loaded
(More sections if required)
00 Block size of 0000h - indicates end of the source program
Figure 6-6. Parallel GPIO Bootloader Handshake Protocol
1 2
Host control
GPIO27
Device control
GPIO26
Copyright © 2012–2019, Texas Instruments Incorporated
3 4 5 6
ROM Code and Peripheral Booting
M-Boot ROM Description
565