def display_block(self, bitmap, row, col, col_count, col_offset=0):
        page_count = bitmap.rows >> 3
        page_start = row >> 3
        page_end   = page_start + page_count - 1
        col_start  = col
        col_end    = col + col_count - 1
        self.command(self.SET_MEMORY_MODE, self.MEMORY_MODE_VERT)
        self.command(self.SET_PAGE_ADDRESS, page_start, page_end)
        self.command(self.SET_COL_ADDRESS, col_start, col_end)
        start = col_offset * page_count
        length = col_count * page_count
        self.data(bitmap.data[start:start+length])