CH Tech EM405D user manual Block Read command

4.3.4.2Block Read command

The Block Read command reads a block of data from an M-module. Unlike the block write command, block read does not have a restriction on the number of bytes that can be read with a single command. The number of bytes read in any given command is equal to:

number of bytes = number of blocks * block size * word size

The block read command consists of nine command bytes. The return value is any number of data bytes followed by a single status byte indicating the success of the command.

Command Syntax:

0x50 md as ws ad ai nh nl bs

Return:

d1 d0 ... SC

where

md = module (0 = invalid, 1 = M-module A, 2 = M-module B) as = address space (0 = I/O, 1 = future use)

ws = word size (2 = 16-bit word, other values for future use) ad = starting address (0 to FF)

ai = address increment (number to increment address by after each write) nh = number of blocks to read (upper 4 bits)

nl = number of blocks to read (lower 8 bits)

bs = block size in words (i.e., number of words per block)

d1 = data (MSB)

d0 = data (LSB)

…= the number of data bytes = ws × bs × number of blocks (nh:nl) SC = Status Code

Example (values shown hex):

To read three data values from a 32-bit FIFO located at I/O Register 6 and 8 on M-module B, send the following command:

Command:	cd	md	as	ws	ad	ai	nh	nl	bs
Send:	50	02	00	02	06	00	00	03	02
Receive:	da1 db1 dc1			dd1 da2 db2 dc2				dd2 da3 db3 dc3 dd3 00 (if successful)

where

dax = MSB of register 6 dbx = LSB of register 6 dcx = MSB of register 8 ddx = LSB of register 8

Note: x = 1 is first read, x = 2 is second read, x = 3 is third read

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